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Tag Archives: Microscopes

A Method of Grinding Small, Spherical Lenses: Spinoza

Van Gutschoven’s Design for Grinding Small Lenses: Letter No. 1147

We have in a letter written to Christiaan Huygens by G. van Gutshoven, descriptions and diagrams of the essential processes for grinding small spherical lenses, as they were likely shared by most contemporaries of the age. The letter is surely a response to a request from Christiaan who may have been in need of smaller lens grinding techniques, either due to his future interest in compound eye-pieces for telescopes, or in regard to the question of the best lenses for microscopes which would later arise in discussions between himself and Johannes Hudde and Spinoza as well. In any case, van Guschoven an Antwerp mathematician, was Huygens’ initial teacher of the complete essentials of lens grinding in the first place, which he gave to him ten years before in a letter dated Feb. 10, 1653. It was by the aid of these instructions, among others,  that Huygens was able to grind one of the most powerful lenses in Europe, and discover the rings of Saturn in 1656.

This letter is dated only as 1663 by the editors of Huygens’s Oeuvres. 1663 was the year that Spinoza had moved to Voorburg, where the Huygens family kept their Hofwijck country estate. That spring Spinoza rented rooms in the home of master painter Daniel Tydeman, but a five minute walk from the Hofwijck. But Christiaanwas not yet there. He was living in Paris with his father who was attempting to curry the diplomatic favor of King Louis XIV, an effort which would result in Constantijn Sr.’s son becoming the secretary to Louis’ Royal Academy of the Sciences, in 1666.

None of this has occurred yet. Christiaan and Spinoza have not yet met (unless they crossed paths momentarily in the summer of 1663, when a traveling Christiaan took leave of Paris to go to London in the off-season). Huygens would not arrive in Holland and develop his relationship to Spinoza until after May of 1664.

What this letter reveals to us though is the basic mechanism and techniques used in the grinding of small lenses. We know that Spinoza made microscopes (and telescopes) at least since the year of 1661, and in his coming debates over techniques and optics with Christiaan he would champion much smaller, more highly curved lenses for microscopes, against Huygens’ designs of lesser magnification. One would think that from van Gutschoven’s descriptions we can receive a sense of the physical practices that preoccupied Spinoza for many of his daylight hours, specializing at times in these smaller lenses.

It should be noted that the Huygens brothers by this time are among the best lens-grinders in Europe, and Christiaan had already worked on several sophistocated semi-automated designs of grinding machines. These instructions must have been experienced as extremely rudimentary to Christiaan (or perhaps, it is from another date).

The letter has three figures, pictured below. The first of these shows a vertical grinding form that is likely of iron or copper. One can see the core movement of a lathe, as foot petal likely drove the strap that turns the shaft, spinning the form concentrically. For larger lenses the form would be hollow, holding the concavity of a curvature that one would want the glass to have. Here though, the small lens is to be ground in the “canal” near its lip:

“Now in this hollowed out canal C D you will grind glasses affixed to a handle and pressed into the canal, with the handle in the hand continuously; while grinding the glass you would turn it until all parts of the glass are equally ground.”

After this equanimity is roughly achieved, attention is turned to the “laminate” or layered strip A B, which turns so the top of it is horizontal to the turner’s bench. By van Gutschoven’sdirection, the laminate is of a soft wood, polar or willow. (Other techniques of the day call for paper.) The roughness of dimples are by hand ground away, and Tripoli, which is a chalky substance made of the remains of microscopic marine life, is added to the laminate to smooth the way.

After this, there is a third process recommended which can either be done in a concave wooden form G H, it too aided by Tripoli, pictured here:

Or, what seems to be a pillow (plombae), affixed to a lathe shaft EG:

There are several things of interest here. The date of the letter makes this description contemporaneous with Spinoza’s own practices, so one might assume a basic correspondence. The grooved canal method strikes one as similar to those a-centric grinding techniques discs used by diamond polishers which Spinoza may have come in contact with either briefly as a merchant of gems, or simply by growing up in a community where gem polishing. The process remained unchanged for several hundred years as late 19th century illustration below shows:

Like the diamond polisher, it is quite possible that Spinoza’s form was oriented horizontally, and not as van Gutschoven suggests, vertically. This was part of a gradual change in lens grinding techniques, much of it initiated by gem polishing influences. The horizontal mould simply made the glass easier to control, and the variable polishes to be administered more cleanly. For this reason, any polishing with Tripoli also occurred on a horizontal, turning wheel. The grinding forms designs that I have seen that the Huygens were using now all had a horizontally oriented lap. 

The second thing to note that in 1667 and 1668, after Christiaan had come to know Spinoza and become familiar with Spinoza’s techniques, he clearly did not still feel comfortable with the limits of van Gutschoven’s design, whenever he had received it, as he in repeated letters urged his brother about the fineness of Spinoza’s small lens polishing. Spinoza’s technique was not that of van Gutschoven. It is my feeling that he had developed, either though his associations in the community he grew up in, those influenced by the practices of gem polishing, means of polishing that were not common to the rest of Europe. Whether these be methods of grit application, the use of diamond dust, particular designs of a simple but effective lathe, one can only surmise. But it seems that Spinoza’s glasses were of a quality and luminosity that made them distinct.

Here is the Latin Text of van Gutschoven’s letter: The Text of van Gutschoven’s Letter to Huygens No. 1148


Aside from this I would want our investigative imagination to extend itself to the physical understanding of these practices, and the conceptual impression they would leave upon a thinking man who engaged in them repeatedly. This has been a theme of my thinking, that if Spinoza had been a potter we may do well to think about his metaphysics and arguments in terms of the potter’s wheel with which he was familiar. The grinding lathe is not so different from the potter’s wheel, and van Gutshoven’s diagrams give us a visual vocabulary for the kinds of effects and exertions that Spinoza produced in perfecting his craft. What in particular these diagrams allow, apart from the general understanding of the grinding lathe, is the picture of a grooved grinding practice, the canal, which varies from the greater method of placing a glass blank within a concave metal form. If indeed Spinoza used this method for his small objectives for microscopes, we can think along with him in the craft of it, and see him bent over the lip of the spinning canal.

As pictured here before, here is an example of a foot petaled lathe from the year 1647, that used by Hevelius. It may give us a dynamic sense of the physical engagement:

Here is a closer look at the Hevelius Lathe: Spinoza’s Grinding Lathe: An Extended Hypothesis


Van Leeuwenhoek’s View of Technology and Spinoza

Part of this process of looking into the lensed conception of Spinoza’s metaphysics is understanding how at the cusp of a change in the technological interface – that is, with Descartes, an increased mathematization of nature and its corresponding instrumentization of devices – there also existed alternate conceptions of what viewing, observing and measuring entailed. The idea that a device could be of a fixed nature, a neutral embodiment of mathematics, and thus could be pointed in any direction, and at any number of objects, revealingly, is an imaginary simplification. Such a conception of device implies a certain invisibility of the mechanism in that the phenomena is simply shown for what it “is”, denuded. It is my sense that Spinoza, in his metaphysical grasp of the consubstantiality of the material and the ideationalas informed by his experiences as a maker of representational devices, and therefore instruments of both the micro- to macrological sort, conceived of instrumentation in a different kind of way. It was a way which may help inform us of our own potentiated relationship to technology. Rather than experiencing the object as simply being “revealed” it perhaps is better understood as staged, framed, part of an assemblage of observation and use. This is what alternate conceptions of technology may help us see.

In the personof van Leeuwenhoek, praised by history for his explorational conception of the micrological, a man who shared with Spinoza a merchant class origin, shunning for the greater part the fame of Scientific standing, we have a clue to something of the inveterate possibilities of instrumental use. I suggest below the example of the intimacy involved in van Leeuwenhoek’s experience of both his devices and his specimens. The “microscope” for him, was not understood, nor felt to be, a mechanism without context.

Pictured here is a composite drawing of van Leeuwenhoek’s “microscope” bringing together the significant features from the few surviving devices examined by Clifford Dobell. It shows boththe rod upon which a specimen needle is mounted, and the parallel plates between which a very fine lens would be inserted. The height of the specimen needle, and its proximity of it to the lens-plates, could be exactly and stably secured by the turn of screws. These devices are incredibly small, actually smaller than is pictured. What is significant about this device, other than its simplicity and size, is that the lens was so very small, its focal length could be less than 1/30th of an inch. The eye must be placed so as to be nearly touching the lens.

Van Leeuwenhoek made nearly five hundred of these palm-sized instruments, and famously was able to achieve magnification so as to vividly see bacteria and protozoa, the first of humankind to do so. Many of the plates were made of silver, and three of them are known to be made of gold, but none of them are in their material finely crafted in detail. They were tiny work-tools by van Leeuwenhoek’s conception. But there is something more about his concept that is important to dwell upon. After his fame had spread, some of the most important personages of Europe came to his merchant’s house in Delft to see these wonders. What is compelling is that he would let people view specimens on devices of only moderate magnification, and not sell a one. The most profound of his glasses, those upon which he made his most spectacular discoveries, he would not even allow a glimpse. People would ask him, bewildered, why would he make so many devices and never sell any. Various theories have arisen to explain this relation between van Leeuwenhoek and the number of his microscopes. Was he saving them up for sale by his daughter when he had passed? Was he secreting away the most precious facts of his observation capacities, making something of a mystery of it?

I think a clue to the number of devices is provided in the 26 samples he had sent to the Royal Society by his devoted daughter upon his death. None of the 26 are actually capable of the serious magnification that he must have attained in other devices, but each arrived, notably with their specimen already attached (the same is true for most of those auctioned off after his passing). The embryo of a Cochineal, or a thread of sheep’s wool, or the spinning organ of a spider’s abdomen was glued upon its requisite needle, perfectly positioned before its lens. One need only hold it up to light. I believe that far from conceiving of his microscopes as neutral devices which could be made machinically in relationship to laws of nature, and therefore could be turned ubiquitously upon any number of phenomena, each device was handmade for what was to be observed. He made so many devices because he had so many things to look at.

Why Did van Leeuwenhoek Refuse to Let Others Look?

Key to this device/object dyad is understanding that the viewing itself must have been a personal, intimate event. The staging of the specimen, the vice-like recursivity with which it was positioned to its glass, a minuscule glass sometimes ground just for that specimen, was an experiential revelation. As mentioned, the eye must be pressed so close as to practically touch the lens. In his most minute observations his microscopes and their specimens formed a circularity of object, means and eye that was physically closed.

There might be very good explanations why van Leeuwenhoek did not allow others – with the possible exception of his daughter, hired draughtsmen, and perhaps even anatomist Ruysch – to look into his strongest microscopic glasses, the obvious being his stated desire for secrecy; but beneath secrecy, most concerting was the likely intensive intimacy involved in these witnessings. And constitutive of this intimacy were two points. First was that Van Leeuwenhoek’s conception of minute observation was dioramic: frame and object met such that the frame was part of the view. It was an engagement. Secondly, because the device was small and could be held in the hand, and the eye was pressed so near, the consciousness of the viewer was a participation with the frame (metal plate and lens) as much as with the object viewed, so much so that there was no anonymity of vision. In a sense, perhaps van Leeuwenhoek came to feel that viewer could no more easily be exchanged with a particular device, than could its specimen. Individual glasses and individual objects matched, as did the eye, and as the magnification became more intense, so did the investment. This, I suggest, is what van Leeuwenhoek was protecting. One could say, just as one could not share dental braces, nor would not share contact lenses, van Leeuwenhoek refused to share the smallest of scopes. They fit his eye and his vision, prosthetically, and in terms of experience, privately. The math was thus affect-rich and context dependent.

(Could it be that there is closely related reason why van Leeuwenhook may have denied the privledge of looking into his strongest lenses? He was, admittedly, very sensitive to criticism. The game of assertion and denial was quiet unpleasant, and it was in part because of this sensitivity that he did not relish the thought of publishing his findings with the Royal Society at first opportunity. It could have been that this sensitivity extended itself to personal experiences as well. Van Leeuwenhoek was gifted. He had not only diligent powers of observation, but also incredibly acute eyesight, far better than even above average. It may have been likely that he had shown others, early on, his strongest glasses, and others simply could not see in them what he could see. His observations were, in a way, personalized to a more specific degree than even already mentioned, not just by context, but by capacity; he could not afford being told that what he saw simply was not there. They were is own assemblage.)

“…you then hold the microscope toward the sky…as though you had a telescope and were trying to look at the stars in the sky through it,”

he wrote of the process of illuminating a specimen. In such a view the conceptions of the linked Macrocosm and the Microcosm collapse into a single relational whole, (for one knew that optically a telescope could be turned into a microscope through a rearrangement of the lenses). But holding a specimen glass up to the light was more than this, it was a person’s investment in observation and device, and the one-to-one context between the specimen and its process of viewing that is exhibited by van Leeuwenhoek and his microscopes. This reflexivity of concept is shown everywhere in his staging choices, but perhaps none so evident as when he had carefully ground a grain of sand in order to see a smaller grain of sand, seeing sand with sand: 

The two grains, one a lens, the other fixed in ratio, were viced into exact proportion. This speaks strongly to a closed and event-specific notion of technology, one which involves the viewer as well. The sand-sand-eye-sky’s light looping form an intimacy which opens up an alternate understanding of what observation is, one where what is being looked at cannot be cut off from its mechanism of viewing, nor from who is viewing. Instead it is a putting of objects, including one’s eye, into relation.

Van Leeuwenhoek, Technology and Spinoza

Van Leeuwenhoek lived but 4 miles from Spinoza in the summer of 1665, and it is not at all certain that he had even invented his viewing glasses at that point in time (the earliest record of his observations come during a trip to England in 1668; and some [Ford for instance] propose that he was originally inspired by Hooke’s Micrographia which would have barely reached Delft in 1665). Yet one imagines that it is quite likely that the history of van Leeuwenhoek’s experiments with glassblowing and lens-craft go back further than our first record of them in regard to his English, chalk-gazing holiday [Ruestow suggests that A.v.L. intimates a date as early as 1659]. It is conceivable that the two lens-grinders were both making lenses contemporaneously, a few miles apart. But the point really is not to establish a personal contact point between van Leeuwenhoek and Spinoza, though they do share a matrix of possible relations, it is rather to suggest a conceptual contact point. They are physically proximate and they are both of merchant families (not a small cultural fact). Each pursued knowledge in a hermited, semi-private way. Mostly, though, they likely embody a conception of technology and lens which was not part of the dominate instrumental conception of device; theirs was one where what is personally made (even if it is an instrument) is not divorced from the circumstances of its use, either by its object, or its witness. What van Leeuwenhoek’s technological conception potentially reveals for the Spinozist, is the thought that despite the prevailing mathematicization of Nature, brought forth by Descartes’ lead, the combinatory experience of observer, device and object remains a determining factor in the meaning of what was discovered. This is something that Spinoza brings out when he speaks of our experience of the Sun being only 200 hundred feet away despite our knowledge that it is much farther and larger (Ethics 2p35s): our essence and the sun’s essence interact to produce the affect of a meaningful, imaginary experience, a kind of phenomenal knowledge, a knowledge which, though inadequate and confused, makes up a greater portion of our world. Simply the crystalizing of the phenomenal image into clarity, making it large and sharp, was not enough for “knowledge” in Spinoza’s view. This was not the “clear and adequate” idea. 

Spinoza’s notion of technology – in that he can be said to have one that we can conclude from his philosophy and assumed to be given through his experiences of lens and instrument making – calls our attention to the continual circumstance of our use, including our affective investments, and to the notion that object, device and eye are part of an assemblage of perception organized by our ideas. More than an ever more crispening of the image is the relation of that precision to our own exactness, and therefore for Spinoza, our own power. The conception is really Cybernetic.