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c. 1838

seed microscope and Raspail scope

This image compares the common 'Seed or Insect' microscope, on the left, to the Deleuil microscope as described by Raspail in 1838 and figured on the right. The figure points out the features of the instrument:
c=cylindrical brass case (cover)
p=object holder (stage)
m'=upright supports to hold the horizontal lens holder, threaded on inside surface
m=the microscope

On this page I will attempt to set the record straight on the original cylindrical microscope described by Raspail in his books and atlas of 1838.

Beginning in the 1950's, various microscope historians, perhaps starting with P. Van Der Star, started to refer to a type of microscope with a glass liner as a 'Raspail' type or a 'Microscope according to Raspail.'   That type of microscope, shown on the left in the figure above, was mostly sold in the last quarter of the nineteenth century by companies like Beck and Queen. Examples of these 'seed or insect' microscopes are shown in detail on the seed or insect microscope page on this web site. They were never attributed to Raspail in any catalog or book of the nineteenth century that I am aware of. It is likely that those that saw the similarity to that one pictured in Raspail's book (image on the right above), did not study the image or the text of these publications carefully, for they would find that the Deleuil instrument was a bit different.

As he described the microscope pictured in the engraving from his book, Raspail explained how this microscope was capable of quality work in the field and how it worked. Important features included that, after being inverted, it screwed into a brass case for travel and that it could be screwed onto this case in the upright position, with the case serving as a handle when in use. It allowed light to enter as most of the cylinder was cut away, leaving only two brass supports. In this way it could be used to view opaque objects. He explained how one could also view a transparent or translucent object secured to the stage (by saliva), by detaching the microscope from its case and holding it up to a cloud or other suitable light source. These features are similar to the seed or insect microscope already alluded to, but additional features prove to be quite different.

While the Deleuil microscope has a stage, the seed or insect microscope has a glass cylinder inside, with the bottom end sealed and the upper end in contact with the eyepiece support. This allowed an insect to be trapped inside the 'seed or insect' microscope. The microscope described by Raspail did not have an interior glass cylinder. Instead, inside it had a glass stage plate with a threaded brass edge which matched the threading on the inside of the two upright supports so that rotating it would change its position up or down. As an option, Raspail described a glass cylinder, open at both ends that could be used to cover the outside of the instrument 'to prevent ones breath or the wind from disturbing the specimen' if desired.   Another difference was the fact that the Deleuil microscope described by Raspail was apparently supplied with three eyepieces of differing focal lengths and therefore variable magnification.

One lens had a focal length of one 'pouce.' The second of six 'lines' and the highest power of one 'line.'   These correspond to focal lengths of approximately 27 mm, 14 mm and 2.3 mm (about 1 inch, 1/2 inch, and 1/10 inch).

In his book, Raspail stated that all the microscopes described in his book were made by Deleuil, with the exception of the horizontal form made by Chevalier. Raspail described two different microscopes in his 1838 book, the one shown in the engraving above being one 'for travel', and a large box-mounted modification of the 'Ellis Aquatic' type which he called a 'Cabinet Microscope.'   the Cabinet microscope could be used both as a compound microscope and also as a simple microscope by changing the housing for the optics on the end of the arm. For a beautiful example of the 'Cabinet Microscope' he described see the example in the Golub collection.   A much smaller microscope, which was referred to as 'Raspail's Microscope' by his contemporaries in the 1830's4, resembles the 'Ellis Aquatic' in size, but incorporates the same arm as the larger 'Cabinet' model. This arm has rack and pinion focusing and also has a forward-backward motion by screw, in addition to horizontal movement in an arc. The forward and backward motion by screw was Raspail's innovation. An example of this type of microscope by Picart is on this site and you can see an example by Deleuil on Allan Wissner's site.

Although there are some features in common, the Deleuil cylindrical microscope Deleuil was a much more complicated and complete instrument than the 'Seed or Insect' type shown to the left above. Deleuil's microscope did not have an internal glass 'cage' but instead had a glass stage, (p in the engraving) surrounded by a brass edging. This stage, or 'object holder,' was threaded on its outer edge to match threading of the inside surfaces of the supports of the microscope, allowing its distance from the eyepiece to vary. This feature, along with a variable focus of the eyepiece itself, allowed a wide range of objects to be studied regardless of their height or thickness. The microscope Raspail described also featured three different magnifying eyepieces, to provide a wide range of magnifications. In the Deleuil model, a glass covering, open on both ends, and not shown in the engraving, was an option to fit over the outside of the cylinder(m). This was designed to be removeable and served to allow observation without interference from ones breathing or the wind, rather than restrain the subject inside. In contrast to this outer glass covering for the Deleuil microscope, the 'seed microscope' had an interior glass cylinder which was closed at the bottom. Some examples of the 'seed or insect' microscope also incorporate a glass disc on the bottom which can act as a compressor.

The 'seed' or 'cage' microscopes pictured on this web site are certainly not of the same caliber as the Deleuil microscope described by Raspail. They have one low powered eyepiece and no moveable stage. Unlike the instrument pictured by Raspail, the inside surfaces of the supports are not threaded on these instruments. They do, however, have a few features in common with the Deleuil microscope. They were, like the Deleuil microscope, designed to allow light to enter from the sides, for better visualization of opaque objects, they can attach to the top of the cylinder as a stand or handle, and they do pack away for storage upside down inside the cylinder. Also, like the Deleuil microscope, the eyepiece has adjustable focusing. These 'seed' or 'insect' microscopes were inexpensive devices intended for very elementary studies, not the more versatile (and more powerful) instrument like that used by Raspail.

I should mention actual examples of the cylinder microscope as actually described by Raspail, and presumably, as made by Deleuil, are not known to exist, at least at the time of this writing(2016).

1. Nouveau système de chimie organique, fondé sur des méthodes nouvelles d'observation. Tome 1 / par F.-V. Raspail... - 1838.
2. Nouveau système de chimie organique, fondé sur des méthodes nouvelles d'observation. Atlas / par F.-V. Raspail... - 1838
3. Nouveau système de chimie organique, fondé sur des méthodes nouvelles d'observation. Tome 3 / par F.-V. Raspail... - 1838
4. See, for instance, Bonnet, in the 1838 London Medical Gazette, and The American Journal of Pharmacy Vol 9, p225, 1839, and many others of the period. This type of microscope continued to be called 'Raspail's Microscope' even in books as late as 1877 e.g. Phin, J. Practical Hints on the Selection and use of the Microscope 2nd Ed. 1877 p27.