American-Made Fresnel Lenses by Thomas Tag
Most people, even most lighthouse enthusiasts, do not know that Fresnel lenses were made in America. The following story will tell how an American glass maker, a disgruntled Frenchman, the need for an astronomical telescope in Japan, $11.95 of erroneous import duty and a strong desire of our government for ‘Made in America’ led to the manufacture of American Fresnel lenses.
A Short History of Optical Glass Manufacture
In 1788, lighthouse lenses, with a diameter of 21 inches and a thickness of 5 inches, were made by Thomas Rogers in England. Rogers’ lenses were made from thick slabs of ordinary window glass of very poor quality with many bubbles and striae - an imperfection in the glass characterized by nearly transparent wavy lines or patches. Rogers ground down the slabs of glass to make his thick lenses. The glass was so poor and the lenses were so thick that the lenses were reported to actually reduce the light output rather than enhance it, and were used in only a few English lighthouses.
In America in 1810, Winslow Lewis made lenses of 9 inches diameter that varied from 2.5 to 4 inches thick. Lewis’ lenses were made from green bottle glass of poor quality. These lenses also reduced the light output and were later abandoned. Better optical glass and new lens designs to reduce the lens thickness would be required before efficient optics for lighthouses could be produced.
Around the world many glassmakers had long tried to make optical quality glass. It was not until around the year 1790 that a Frenchman, Pierre Louis Guinand (1748-1824), invented the first truly successful process and set of ingredient formulas for the production of optical glass. Prior to this time, it was only possible to produce optical quality lenses with a diameter of about three inches. By 1790, Pierre Guinand was able to make optical quality lenses of up to nine inches in diameter with his new process.
Pierre Guinand’s secret process involved the use of a two-foot long stirring rod made of fire-clay. This rod was used to stir the molten optical glass mixture within the furnace, to produce a homogeneous glass that was nearly free from bubbles and striae. Pierre Guinand kept his process and list of ingredients closely guarded, as did each of the other glass manufacturers at that time. In 1805, Pierre Guinand joined with two German optical glassmakers, and together they developed the manufacture of optical glass in Germany.
Pure optical quality glass could only be made in small batches and was very difficult to work. The lighthouse lens designers and glassmakers chose to use a form of Crown glass produced from only the purest ingredients, using special furnaces, and using many of the optical glass manufacturing techniques, such as the stirring rod to reduce bubbles. With these processes they were able to create a near optical quality Crown glass, for lighthouse lenses that remained relatively easy to manufacture and form into lens elements.
In 1819, another Frenchman, Augustin Fresnel began his design of lighthouse optics resulting in the now famous Fresnel lens, first installed in the Cordouan lighthouse, in France, in 1823. His was the first use of near optical quality glass and advanced lens design principals in a lighthouse lens. Fresnel’s first production lenses were constructed by François Soleil with glass from St. Gobain, and had an index of refraction of 1.51.
During this time, Monsieur Soleil and one of Pierre Guinand’s assistants, Monsieur Bontemps, continued optical glass production in France and were able to produce single lenses with a diameter of fourteen inches in the year 1828. Later, in 1848, Monsieur Bontemps went to work for Chance Brothers in England where he was essential to Chance’s manufacture of optical glass and lighthouse lenses.
In 1852, John L. Gilliland, of the Brooklyn Flint-Glass Company, patented a method of using pressed and molded Flint glass for lenses. The Brooklyn Flint Glass Company made small Fresnel bull’s-eye lenses for use in railroad lamps, steamboat and dock lamps. They proposed the use of their lenses for lighthouses and in 1858 they produced a very small number of pressed Flint-glass sixth-order lenses. These were the first Fresnel style lenses made in America. The quality of the pressed Flint glass was not as good as the ground and polished Crown glass used in Europe.
Amory Houghton Sr. started in the glass industry in 1851 and in 1864 he purchased the Brooklyn Flint Glass Company. Houghton moved the company to Corning, New York and established the Corning Flint Glass Works on October 22, 1868. This company was incorporated as the Corning Glass Works in 1875. Corning Glass later produced Fresnel drum style lenses.
In the 1850s, Charles Feil, a grandson of Pierre Guinand, founded his own glass factory in France and continued the family tradition of optical glass making there. In 1872, he placed his company under the direction of his son Edmond Feil. Under Edmond’s leadership, or lack thereof, the Feil Company floundered within a few years, and Charles had to regain control. Edmond Feil left his father’s business and started his own very small optical lens factory. By 1885, Charles Feil took his son-in-law, Edouard Mantois, as a partner and they jointly ran the business until early 1887 when Charles died.
Edmond Feil thought he would return to the business as a partner on his father’s death, but he was left out of the partnership contracts and Monsieur Mantois took over as sole proprietor. Edmond Feil was devastated, and became quite vindictive. He immediately wrote to Chance Brothers in England and offered to sell them the processes and ingredient formulas for many types of optical glass then produced only in France and Germany.
Chance Brothers accepted Edmond’s offer and purchased drawings of various glass making tools and molding equipment, as well as all of Edmond’s, formerly secret, glass formulas. In addition, Edmond Feil made it generally known throughout the glass industry that he was available for hire or consultation. In 1890, George Macbeth brought Edmond to America as the general manager of his new glass factory located in Elwood, Indiana, which was then under construction.
George Macbeth began his career in glass making in Pittsburgh Pennsylvania in 1872 with the manufacture of glass chimneys for oil lamps and became one of the world’s largest producers of lamp chimneys by 1880.
In 1899, Macbeth Glass merged with the Thomas Evans Glass Company to form Macbeth-Evans, which then became the world’s largest producer of lamp chimneys, and major manufacturers of a variety of other glass articles.
George A Macbeth
First Optical Glass Made in America
The Spencer Lens Company and the Lennox Glass Company both tried to make optical glass in the 1860s, but could make only very tiny quantities of rather poor glass. In 1890, George Macbeth built a glass factory in Elwood, Indiana. Elwood was chosen because a very large source of natural gas had just been found in the Elwood area, which could fuel the glass melting furnaces.
The Elwood plant was specifically designed to produce large quantities of lamp chimneys, but Macbeth had always had a fascination with optical glass and he devoted a special room and one-pot furnace to its production. The plant was completed early in 1891. On August 5, 1891, Macbeth organized a special train that picked up 365 of his workers, their families and household goods in Pittsburgh, Pennsylvania and moved the workers and Edmond Feil to Elwood, Indiana. The factory then began lamp chimney production and Feil, in addition to his management duties, began making very small experimental batches of optical glass.
Later in 1891, an astronomy equipment manufacturer, and friend of George Macbeth, named John Brashear, was working on telescope lenses to be used in the Tokyo Observatory in Japan. An accident occurred in the grinding process and several lenses were destroyed. The lens glass John Brashear was using had been imported from France and it would take several months to receive a replacement order. Brashear went to Macbeth and asked if there was any possibility of obtaining replacement lens glass in America. This was just the opportunity George had been looking for. He contacted Feil at the Elwood plant and discussed the project. They decided they would try to produce the lenses at Elwood. Production quantities of materials were immediately purchased, and within a few weeks Feil made his first attempt at producing the lens blanks. The first glass produced was perfect and the lens blanks were quickly made and sent to the grinding process. John Brashear was elated and immediately gave Macbeth orders for glass lens blanks for eventual use in the telescopes being built for the Gill Observatory in South Africa, Dudley Observatory in New York, Princeton Observatory and others.
No other American company was then able to make high quality optical glass in quantity, for use in instruments, lenses, and laboratory equipment. The plant eventually produced Flint glass as well as other specialty optical glasses.
Macbeth won a prize at the Columbian Exposition in 1893 for producing the first high quality optical glass in America. Although no records exist, it was probably at this exposition where Macbeth was first approached by the U.S. Lighthouse Service in regard to the potential manufacture of Fresnel lenses. The Lighthouse Service had a large display at the exposition, and various Lighthouse Board members were probably visitors.
Unfortunately, the production costs of American labor could not compete, at that time, with those in Europe. After only five years of very limited production, Edmond Feil left the Macbeth Company and the production of optical glass was stopped. However, optical glass research continued and experimental batches of optical glass were still produced.
Enactment of a Tariff on Optical and Near Optical Quality Glass
On June 10, 1890, Congress passed a Tariff Act that provided:
“Duties shall be collected on Lenses of glass or pebble wholly or partially manufactured and not especially provided for in this act, at 45 per centum ad valorem.”
This Act caused an immediate cost increase for all Fresnel lenses imported by the Lighthouse Service.
The Lighthouse Board reacted by requesting an increased appropriation for ‘Supplies of Lighthouses’ in 1891 and they also added the following to their request:
“Heretofore certain articles of lighthouse supply not manufactured in this country were imported duty free. Under the present tariff act duties must be paid on them. This will be an additional drain upon this too slender appropriation. Thus it will be seen that with the means at hand it will be necessary to practice the severest economy to keep the present lights properly supplied.”
In addition, they requested an increase in the appropriation for ‘Repairs’ and added the following:
“The cost of duties laid by the new tariff act upon illuminating apparatus and other material, which was formerly admitted duty free must be met.”
A similar statement relative to ‘Supplies of Lighthouses’ was made in the request for appropriations in 1892.
The Lighthouse Board was also quietly lobbying Congress to make an exemption to the tariff for optical glass used for lighthouse purposes. In early 1893, they were successful and the Act of March 3, 1893 for ‘Supplies of Lighthouses’ was passed stating:
“It is provided: That lenses and lens glass for the use of the Lighthouse Establishment may be imported free of duty.”
Fresnel lens costs returned to their actual price, saving the Lighthouse Service 45 percent. This happy status remained in effect for the next eight years.
Lieutenant Colonel David Porter Heap 1843-1910
Then it happened! In late 1900, Lieutenant Colonel D. P. Heap who was Engineer of the Third Lighthouse District and in charge of the Lighthouse Depot at Tompkinsville, NY, ordered some lens prisms from France to repair a damaged lens. The prisms were shipped to New York in January 1901, by the American Express Company. When they arrived, the local customs agent was apparently told only that the package contained optical glass, and he then requested $11.95 for the optical glass duty, which was paid by the American Express Company. Lieutenant Colonel Heap did not find out about the erroneous charge for several weeks until the American Express billing arrived. He then made his first mistake. Heap wrote to the Lighthouse Board requesting that the government refund the $11.95.
Lieutenant Colonel Heap should have known better. Although he was a member of the US Army Corps of Engineers, he had been assigned duty in the Lighthouse Service since 1880 where he had been the Engineering Secretary of the Lighthouse Board from 1883 through 1887 and was assigned as the Third District Engineer from 1887 through 1894 and again starting in 1897. He should have realized that bureaucrats don’t like paperwork and especially don’t like to fill out numerous forms and letters for insignificant sums. Heap’s letter was forwarded to the Treasury Department who promptly rejected the request. Unfortunately, that did not stop Heap. He again wrote a letter requesting a refund, this time to the Assistant Secretary of the Treasury who replied as follows:
“In reply I have to state that, while the articles were entitled to free entry under the said provision of the law, there is no provision of law under which refund of the duties paid as aforesaid could be made in the absence of a timely written notice of dissatisfaction to the collector of customs at New York, under the provisions of section 14 of the act of June 10, 1890. Your application is therefore again denied.”
Now, Heap made his big mistake, he again wrote a letter to the Treasury Department as follows:
“I now request to be advised if I can reimburse the American Express Company for duty paid under misapprehension -- this reimbursement to be charged against the appropriation from which the cost of the prisms was paid.”
This time the response from Treasury was not what Heap expected. The response was written on June 21, 1901, directly by R. J. Tracewell, Comptroller, who agreed to Heap’s request, but also added a long dissertation about the original wording of the Act of March 3, 1893, concluding as follows:
“I am therefore of the opinion that neither the language nor the nature of this proviso indicates an intention to enact general and permanent legislation, and that it must be construed to be limited in its operation to the particular appropriation of which it forms a part.
Adopting this construction, it follows that duties were legally exacted, and you are therefore authorized to reimburse the express company for the amount thereof paid by it to the Government”
This meant that in the Comptroller’s opinion, the original 1893 provision should have ended at the end of that fiscal year, and the free importation of optical glass by the Lighthouse Service was at an end, unless Congress re-worded the language of the Act of 1893 and reenacted it into law. Based on this finding the customs collectors were advised to start collecting the tariff on ALL optical glass from June 21, 1901 forward.
On July 24, 1901, the Lighthouse Board sent Lieutenant Colonel Heap a telegram as follows:
“Report at once by letter, all illuminating apparatus ordered from abroad, which manufacturers were informed was subject to free entry. Name Firms.”
The Lighthouse Board was really upset and began lobbying Congress to re-write the act. Lieutenant Colonel Heap was ordered relieved of duty in the Lighthouse Service on August 9, 1901, and returned to the US Army Corps of Engineers, serving in California. The Lighthouse Board also got the Secretary of the Treasury to write a letter to Congress on January 30, 1902, asking that the act:
“be modified, reenacted, and made part of the next sundry civil appropriation act in that part relating to repairs, etc., of lighthouses...”
For some unknown reason, the Congress refused to add the requested new wording, and beginning in 1902 and for the next five years, the Lighthouse Board’s Annual Report carried the following request:
“Free entry asked for goods imported for lighthouse purposes.”
But, this was all useless activity, as Congress failed to respond and the tariff duty continued to be collected.
At the same time, another major change was underway for the Lighthouse Board. From its inception, the Lighthouse Board had been under the Secretary of the Treasury and the Treasury Department. On July 1, 1903, the Lighthouse Board was transferred to the Department of Commerce and Labor. The combination of the increased costs from the re-imposed tariff and the pressures of being under new management set the Lighthouse Board in action to find an immediate solution. The Lighthouse Board began to solicit American glass manufacturers about the possibility of developing the capability to produce near optical quality glass and the needed Fresnel lenses in America.
The September 26, 1903 issue of Scientific American reported:
“The United States Government has afforded experts in this country every opportunity to learn the art of making Fresnel lenses, but up to the present without success. One of the most prominent American optical firms was given one of these lenses to copy, but after nearly a year of experiment was obliged to abandon the attempt. Consequently, Uncle Sam has to send abroad for his lighthouse equipment. The same holds true in the mounting of the lenses. This is also done abroad, so that whenever a lens is broken it must be shipped back to Europe for repairs.”
No American firm would take up the challenge, and the Lighthouse Board continued to buy from abroad, at ever increasing cost, including the tariff duty. Over the next few years additional attempts were made to find an American supplier, without result. Additionally, in 1909 Congress decided to restructure the Lighthouse Service and they passed a law, which took effect on July 1, 1910, terminating the Lighthouse Board and replacing it with the Bureau of Lighthouses under the leadership of Commissioner George Putnam.
Development of Navigational Aids at Macbeth-Evans
In 1910, the Lighthouse Bureau approached Macbeth-Evans and requested that they evaluate the possibility of producing a small fifth-order Fresnel lens for use on American lightships. By this time, Macbeth-Evans was back in limited production of near optical quality glass and was looking for a project with a continuing need for relatively small quantities of the glass, and while American labor costs had not come down, the use of sophisticated grinding and polishing tools, design for part interchange and advanced production processes were in place, lowering overall costs.
Macbeth-Evans accepted the Fresnel lens project and started an evaluation of all parts of the design and construction of such lenses, as well as the composition and manufacture of the lens glass.
The glass used in all of Macbeth-Evans lenses was different from that used by the European makers. Macbeth-Evans used glass with an index of refraction of 1.55 versus the European standard of 1.52, and a specific gravity of 2.95 versus 2.52 for Europe. The glass was known as non-hygroscopic, meaning that it does not absorb any moisture. It was a heavy, brilliant glass with a very slight gray color, and it would take a finer polish than European glass. This type of glass was harder to make, especially without bubbles and striae.
Macbeth-Evans lenses were also improved over European lenses in their physical design. George Macbeth hired Professor Harry S. Hower, of the Carnegie Institute of Technology, to design the prisms used in his lenses. Professor Hower noted that in European prisms only one of the sides of the prisms was slightly curved, which improved its ability to direct the light as needed. The Macbeth-Evans prism design was constructed with two conical surfaces and the third surface was a hyperboloid of revolution giving still more enhanced light throughput and control. This structure was more complicated than any other manufacturer had successfully produced, and Macbeth-Evans lenses were found to transmit as much as 50 percent more light than the European lenses of the same type and size.
The Macbeth-Evans prisms were manufactured completely by machine. The grinding and polishing equipment was developed by Mr. Heupel, the Macbeth-Evans manufacturing engineer, and allowed highly accurate and lower cost manufacture. Mr. Heupel also developed designs for all of the brass-work that was used to create the finished lens panels. This brass-work was held to very high tolerances, which reduced the cost for the initial setup and testing of the lenses.
Red Glass for Use in Characterizing Lighthouses
The European glassmakers used ruby glass made by adding gold to the molten glass mixture. Ruby glass was produced in panels for use external to the Fresnel lens, and ruby glass was also formed into lamp chimneys. Ruby glass provided the red color used to create part of the lighthouse’s characteristic and to mark dangerous areas. Unfortunately, ruby glass is brittle and very easily broken, and the European panels were generally made at least one-quarter inch thick to reduce breakage. Ruby glass absorbs approximately seventy-five percent of the light passing through the red panels. This is due to the fact that only the red light rays and some useless blue light rays pass through and also due to the thickness of the glass panels, which absorb many of even those light rays.
Beginning in 1911, the Lighthouse Bureau asked Macbeth-Evans to produce red glass panels and chimneys, however, Macbeth’s glass was specifically designed to have a red-orange color, and the color was produced with chemicals other than gold, allowing the glass to be made far less brittle and consequently to be produced with reduced thickness. The Macbeth-Evans red-orange panels and chimneys absorbed less than sixty percent of the light, giving a more powerful light for mariners.
Fresnel Lenses and Other Navigational Aids Made by Macbeth-Evans
The 187.5 mm. fifth-order 3 panel fixed lightship lens was the first lens attempted by the Macbeth-Evans Company. The first lens was successfully delivered to the Lighthouse Bureau in 1910. In 1912 Macbeth-Evans agreed to undertake the development of fourth-order lenses. By the early part of 1913, Macbeth-Evans produced their first fourth-order lenses and ‘Made in America’ became a reality.
Products:
150 mm. Cut glass Buoy lenses
200 mm. Pressed glass Buoy lenses
300 mm. (150 mm. Focal length) sixth-order 3 or 4 panel fixed Pressed Glass Buoy Lens, ground on inside
187.5 mm. Fifth-order Range Lens
250 mm. Fourth-order Range Lens
250 mm. Fourth-order Bivalve Lens - 4 segment
250 mm. Fourth-order Bivalve Lens - 5 segment
250 mm. Fourth-order 6 panel Fixed Lens
250 mm. Fourth-order 4 panel Flashing Lens
187.5 mm. Fifth-order 3 panel Fixed Lightship Lens
Mangin mirror reflectors 225 mm. Radius spherical silvered mirrors with 60°, 90°, 120° sectors
250 mm. Fourth-order Dioptric Cylindric Lens
187.5 mm. Fifth-order Flashing Lens (not shipped)
Red-Orange Glass Panels
Red-Orange Lamp Chimneys
“New types of reflectors made of glass with reflecting surface on the back, have also been placed in service.”
Views of the Lighthouse Bureau
Lighthouse Service Bulletin No. 17 from May 1913 states:
“Until recently it has been necessary to procure all the cut-glass lenses used in the Lighthouse Service from France, England, or Germany, most of them coming from France. The making of a lighthouse lens has hitherto been largely a matter of manual labor, and, as labor abroad is cheaper than in this country, the American manufacturers have declined to compete with foreign makers.
Recently the matter has been taken up with an American firm of glass manufacturers with the idea of ascertaining if a better lens could not be made in this country than abroad by using some modern manufacturing methods. The first lenses made were 187.5-mm. radius, or what is known as the fifth-order, and they were so successfully made that there are now being manufactured a number of fourth-order fixed and flashing lenses. The first one of the last lot has been delivered to the general depot and when tested was found to be superior to foreign lenses and can be made for the same cost or less than those furnished from abroad. The glass is hard, white, and brilliant and will keep its polish much longer than the soft glass previously used. The prisms are regular, sharp, and fit close into the frames, and the frames are designed to give maximum strength and rigidity with least obstruction of light.
The essential feature of the American method of manufacture is that the prisms are formed by machines instead of by hand. Every part is made to fit an accurate template or jig so that they are true to size and parts of the same number are completely interchangeable.
It is hoped in a short time that the American factory will be equipped to furnish all lenses except those of large size, where the demand is so small as not to warrant the large equipment cost necessary.”
An internal letter of the Lighthouse Bureau dated June 26, 1913 and signed by Mr. Bowerman, Chief Constructing Engineer, makes the following statement:
“There are now in the old lamp shop two 4th order range lenses and the parts of other 4th order lenses, made by the Macbeth-Evans Glass Co., of lead glass prisms, cast in iron moulds and ground and polished. They are beautiful specimens of lighthouse lenses and Mr. Haskell claims that they are more correctly cut and set than the soda glass prisms made abroad. I understand that Mr. Macbeth has taken a great interest in these apparatus and has spent considerable sums of money in perfecting them and they have already excited the interests of the old manufacturers abroad. They are made from his pearl glass stock, the index of refraction is about 1.56, according to Mr. Haskell, and the only thing about them in anyway detrimental is the presence of a number of air bubbles about 1/16 diameter scattered through the prisms. I understand that Macbeth has sold the Service lenses at $300, which cost him $800 to make. I think he should be encouraged to go ahead, and if the photometric and other tests show them to be equal or superior to the foreign article, it is a matter of satisfaction to all concerned.”
End of an Era
Unfortunately by the time Macbeth-Evans developed the capability to produce Fresnel lenses, the major lighthouse construction era had ended and there were few orders. Macbeth-Evans built very small quantities of Fresnel Lighthouse Lenses and a considerably larger number of buoy lenses, during the period from 1910 to 1932. Macbeth-Evans also built most, possibly all, of the fourth-order range lenses used along the Panama Canal.
Total Lenses Built: (These are all of the lens orders that could be identified. There may have been a few more orders that were not found. Does not include those at the Panama Canal)
Basic Orders Identified Receiving Locations
(8) Fourth-order 6 panel fixed (1) Light Vessel No. 94 (1) Miah Maul Light
(16) Fourth-order 4 panel flashing (1) Light Vessel No. 95 (1) Alki Point Light
(3) Fourth-order 2 panel bi-valve (1) Slip Point Light (1) Avery Rock Light
(1) Liston Front Range (1) Point Judith Light
(1) Cape Flattery Light (1) Reedy Island Range Light
Current Lens Locations:
Type Current Location
6-Panel Fixed White Pine Village Museum, MI
6-Panel Fixed Charlotte-Genesee Lighthouse Museum, NY
6-Panel Fixed US Lighthouse Society on loan to New Dungeness Lighthouse WA
5-Panel Flashing Clalliam County Historical Society, WA (3 Flash Panels 2 Brass Doors)
4-Panel Flashing Calvert Marine Museum, MD
(2) 4-Panel Flashing Shore Village Museum, ME
4-Panel Flashing Sleeping Bear Dunes State Park Museum, MI
2-Panel Bi-Valve USCG National Aids to Navigation School, VA
1-Panel Range Reedy Island Rear Range, DE
Unfortunately, optical lens manufacture was never a significant part of Macbeth-Evans business. However, they were very proud of their being the only U.S. manufacturer with these capabilities and the government was very happy that importation was no longer required except for lenses of the first through third orders.
At the end of 1936, Macbeth-Evans Glass Company merged with the Corning Glass Company and in 1938 the Elwood plant was closed and sold.
Lens Work by the Tompkinsville Lighthouse Depot and Others
375 mm. Pressed-glass Buoy Lenses
In Lighthouse Service Bulletin No. 60, from December 1916 it was reported:
“Experiments have been carried on for some time at the general lighthouse depot, Tompkinsville, NY with a view to the manufacture of 375 mm. pressed-glass buoy lenses for use in place of the present expensive cut-glass lenses. The third inspector now reports that pressed-glass lenses, which from practical tests both with the naked eye and with the photometer have proven of equal efficiency to the cut-glass lenses, can be made for about $150 each, a saving of $250 over the cost of the cut-glass lenses. The pressed-glass lenses will be adopted for use in all 375-mm. lanterns purchased hereafter.“ The 375-mm. Buoy lenses were made by Corning Glass beginning in 1916.
Other glass companies produced Buoy lenses or lens parts for the Lighthouse Bureau as follows:
Corning Glass 200 mm. Pressed, 300 mm. Pressed, 375 mm. Pressed
McKee Glass 200 mm. Pressed
AGA 200 mm. Pressed
Lovell-Dressel Co. Lens frames and lens assembly
After 1932, there is no indication of additional lens orders for other than Buoy lenses, although a few repair panels for the lighthouse lenses may have been purchased. Thus, the era of American lens manufacture ended, and by the 1960s lens manufacture around the world was also severely curtailed. Today, cut-glass Fresnel lenses are, for the most part, a museum curiosity.
