Vintage Visits: The First Patented Microscope, Part 2

In Part I of this article, we reviewed George Lindsay’s simple microscope, the first ever patented microscope. In our review, the authenticity of one of the magnification sliders that came with our Lindsay microscope came into question. The image below shows a vintage Lindsay magnification slider (top) compared to the magnification slider (bottom) that came with our Lindsay simple microscope. Based on historical research we concluded the six-lens magnification slider is a replica. And a bad one at that.

The magnification sliders are strikingly different in appearance, which got us thinking about potential differences, if any, in their elemental composition. We examined both magnification sliders using scanning electron microscopy and energy dispersive x-ray spectroscopy (SEM/EDS) and analyzed other metallic parts of the Lindsay simple microscope. We also tried some low-tech methods to see if they would yield useful results. We’ll start with the low-tech methods.

The Uniform Thickness Test

Modern brass production can often achieve uniform thickness typically not seen in the brass used to construct early scientific instruments. Vintage brass, like the kind George Lindsay used to construct his simple microscope, has a higher degree of variation in thickness due to the manufacturing methods of the time.

In the article “All that Glitters is Not Gold”, published in the Scientific Instruments Society Bulletin, No. 21 (1989), the author, David Weston, tells the reader, dating metals can be tricky, but measuring the thickness of the brass is a good indicator of authentic brass.

“The thickness of the metal is often a good test…if it is of perfect uniform thickness, it is unlikely to have been made by hand.”

Weston goes on to explain when trying to date brass using modern scientific methods, things get more complex because of an abundance of available vintage brass:

“Brass used to be a much more valuable metal than it is today, and it was rarely thrown away but instead melted down for re-use. Most scientific methods of metal dating can give an idea of the age of brass but cannot tell if it has been recast later. There is plenty of old brass for the fakers to work on.”

With Weston’s thoughts in mind, we purchased from Electus Technoventure Limited a length of modern brass sheet rolled metal foil plate with a thickness of 0.5 mm. For modern brass, thickness variation is generally controlled but can vary based on the specific manufacturing method, dimensions, and grade of the brass.

Thickness comparisons of the modern brass sheet to some of the flat brass components on our Lindsay simple microscope were made. We focused on the microscope’s accessories which were long and flat enough to make multiple thickness measurements. This included the folding feet of the microscope’s base and the brass fish plate, both measuring about two inches in length. For comparison we cut a similar length from our modern rolled brass sheet.

To measure the thickness for each of our brass pieces we used a Starrett 799 Electronic Caliper. The caliper can be set to measure in inches or millimeters. We chose to measure the brass components in millimeters.

Using the Starrett electronic calipers is straightforward: open the jaws, insert the object to be measured, gently close the jaws until they stop, and read the digital display. Ten measurements were taken along the length of each of the flat components of the Lindsay simple microscope and compared to those of a modern rolled brass foil plate.

The results show the vintage Lindsay brass components exhibiting significantly more variation in thickness compared to the uniformity of the modern brass foil.

Magnification Sliders

The vintage Lindsay magnification slider and the replica magnification slider are both made using two flat pieces of brass held together by brass screws. Making meaningful thickness measurements of the magnification sliders didn’t seem possible given their two-piece design.

Pinpointing Materials

Our idea of using modern analytical instrumentation to help characterize vintage scientific instruments is not a new one. Jon Darius, editor of the Scientific Instrument Society Bulletin, No. 21, proposed the same idea over thirty-five years ago. In his editorial, Darius lists five areas of future research, among them he describes the need for a more comprehensive materials analysis of vintage scientific instruments:

“First, I would like to pinpoint materials. We simply do not know enough about the composition of instruments of metal and glass…we do not yet have enough comparative data to know how to use the analyses properly. If two alleged 17th-century bronze sundials yield very different quantities of copper, tin and trace elements, we cannot jump to the conclusion that one might be genuine and the other must be misdated or fraudulent. It depends on the degree of intrinsic scatter in the composition of 17th-century melts, which may or may not be a well-behaved function of time and place. The same could be said…of glass, whose character evolved radically in the later 18th and early 19th centuries; but its analysis is fraught with even greater difficulties. More measurements of more instruments are vital.”

More Than Just Brass

If we had to put a rough percentage on the different metals George Lindsay used to construct his simple microscope, the brass components would make up about ninety percent of the microscope, followed by a few silver components at nine percent, and iron components coming in at one percent. Our analysis was limited to the parts of the Lindsay simple microscope which could physically fit into the sample chamber of the JEOL JCM-7000.

Both magnification sliders were placed onto carbon tape attached to an aluminum SEM stub, creating a conductive pathway for the sample. An elemental qualitative composition analysis was done using energy dispersive x-ray spectroscopy (EDS) collected at 15kv.

The elemental composition of both magnification sliders was similar, forty-plus percent copper, around twenty percent zinc, and a trace of lead. It is common to find low percentages of lead in vintage brass, which was sometimes introduced as an impurity during production. Below is a quote from R.L. Barclay’s article “The Metals of the Scientific Instrument Maker” published in the Scientific Instruments Society Bulletin No. 39:

“The brass from certain regions was found to be better for casting, but less easy to cold-work by deformation. This is related to the amount of lead in the alloy, which in turn can be traced to either inadequate purification of the copper, or the addition in the brass-making process of so-called ‘tutty’ or furnace calamine. This is zinc oxide derived from the smelting of lead, and while cheap…it does have the effect of introducing lead as an impurity.”

The lack of elemental differences between the two magnification sliders is not surprising if we go back to David Weston earlier comment, “There is plenty of old brass for the fakers to work on”.

The Other Brass Components

We analyzed some of the other vintage brass components of the Lindsay simple microscope. Again, our analysis was limited to the items which could be physically fit into the SEM chamber. The remaining brass components analyzed were the two-piece stand, the three feet of the tripod base, and the fishplate. Each of these items had a similar elemental composition as the vintage magnification slider, except for trace amounts of tin found in some of the microscope’s stand pieces.

The modern brass foil has a significantly higher percentage of copper and zinc as compared to the vintage brass microscope components, with no traces of lead or tin.

Silver Components

There are several silver components on the Lindsay microscope including focal length indicator scale (indicated by the red arrow), the two Lieberkühns, and the microscope’s name plate.

Iron Components

There are three small components on the Lindsay simple microscope made of iron, the sample holder needle, a support pin built into the top portion of the stand, and the focal length indicator claw, which slides along the silver focal length indicator plate. R.L Barclay describes the limited but specific role steel components played in the manufacture of scientific instruments in his article The Metals of the Scientific Instrument Maker Part II: Steel published in the Bulletin of the Scientific Instrument Society No. 40, …

“Steel was used in smaller quantities than brass, and usually where hard bearing surfaces, greater strength, or good wearing qualities were required…Its chief virtue was its ability to hold a very fine or sharp edge…”

The areas where George Lindsay used iron in constructing his simple microscope supports Barclay’s observations.

Glass Components

The lens components of each magnification slider were analyzed by SEM/EDS and were found to be similar in elemental composition.

Analysis of the Wooden Box

The wooden box, which houses our Lindsay simple microscope was analyzed using Direct Analysis in Real Time Mass Spectrometry (DART-MS). As mentioned in Part 1, our Lindsay wooden microscope box is missing the inside segmented velvet lined compartments as well as the decorative fishskin outer wrapping. The box appears to be genuine based on its size, shape, and positioning of the attached hardware (hinges and lock) as compared to the woodblock print from a vintage Lindsay pamphlet pictured below.

Some publications describe the Lindsay wooden box as mahogany, while others refer to the box as simply wooden. A darkly stained wooden microscope box may sometimes be referred to generically as mahogany based on its color. On the inside of our Lindsay wooden box was a detached fragment from the front upper “lip” of the box. The fragment of wood is pictured below and provides enough sample to be analyzed using the DART-MS.

The resultant spectra were compared to a library of authenticated wood samples and their overall chemical profile. The most likely candidate of the wood used to create our Lindsay box is pine, but there are some concerns regarding possible contaminants in the spectra. There are noticeable repairs and restorations made to portions of the wooden box which may contribute to erroneous DART-MS results.

While the DART-MS technology looks promising for the analysis of wood, there is additional work to be done to apply this technique to smaller sample sizes.

We have learned a lot about the materials George Lindsay used to construct his one-of-a-kind simple microscope. Our goal was not to present a definitive analysis, but rather to open a dialogue with collectors, historians, and the microscopy community, inviting new questions, insights, and further testing. As Jon Darius aptly noted, “More measurements of more instruments are vital.” We couldn’t agree more, especially when it comes to such exceptionally rare vintage scientific instruments.