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Tag Archives: Stan Verdult

Spinoza’s Grinding Lathe: An Extended Hypothesis

Johannes Hevelius, also, Johannes Hewel, Johann Hewelke, Johannes Höwelcke or Jan Heweliusz (January 28, 1611 - January 28, 1687)

A Proposed Homologue to Spinoza’s Grinding Lathe

It has been revealed by some digging into the record by Stan Verdult that indeed the lathe that occupies the Rijnsburg Spinoza museum is not of the sort Spinoza would have used (though it may give us a sense of the size of his lathe). [Written about here: The Rijnsburg Lathe: Like the Sun, not 200 Feet Away .] But if we are to come close to understanding the near-daily physical practices Spinoza had engaged in as a lens-grinder and maker of both telescopes and microscopes, we need to narrow the view to the design parameters his grinding lathe likely exhibited. I have mentioned in the past that the foot-driven lathe of Hevelius, as published in his astronomical study of the moon, Selenographia (1647), provides us perhaps of the most revealing illustration of the elements that would have been involved.

We know from Spinoza’s comments on the semi-automated designs of Christiaan Huygens whose home in Voorburghe certainly seems to have visited multiple times, that Spinoza favored a simple grinding mechanism, one in which the glass to be ground was held freely in the hand (affixed to a handle). The general disposition among mid-century savants to further automate the grinding process and remove the human element from the process as much as possible seems to have been looked on withextreme doubt by Spinoza. This does not mean that there was no automated aspects to Spinoza’s lens-lathe, for the lathe itself is a machined dynamic which transfers motions by the hand or the foot to a concentric movement put upon the glass blank. It is only that Spinoza preferred the moment-to-moment, lived craft judgments that came from an artisan’s practice through the encounter withthe machine. In this way our focus should be upon the nature of the machine/human interfaces used by Spinoza, and therefore a central question is whether Spinoza used a hand-driven or foot-driven lathe, with a view to visualizing each as vividly as possible.

Foot-driven lathes were not uncommon in the era, in fact Hevelius’ Illustration of his lathe was published when Spinoza was 15 years old, perhaps a decade before his reported lens-grinding days, and likely was not seen as an innovation then. I suggest that it is to this illustration we must turn if we are to get a clear picture of the kind of physical actions Spinoza trained his eye upon.

the lathe as it appears in Heveliuss Selenographia

the lathe as it appears in Hevelius's Selenographia

In the labeled illustration below, one can see the general action of the foot pedal transfer of power to a concentric motion, and the orientation Spinoza may have had, and the pole that may have been fixed to the ceiling of his room:

Here are various details so as to better see the composition of components:

Here one can see the transfer of the cord to a grinding form’s modular base. It would not be necessary, or even likely that this modularity would be a feature of Spinoza’s lathe, but the horizontal orientation of the grinding dish (as opposed to the vertical angle shown in designs from earlier in the century) would be the preferred design, for this would allow gravity to act as ally in abrasive control and arm fatigue. (We do not know how intermittent Spinoza’s tuberculosis was, a disease that he, by Colerus’s account, suffered from since about the age of 24, but the question of endurance could have been a singificant factor in the kind of lathe Spinoza used.)

In this close-up to the foot pedal one can see the simple nature of the drive mechanism. A foot pedal allows of course one to use the larger leg muscles, a benefit for more arduous projects; but it also informs a vertical tension from the floor to the ceiling. There is a cross dynamic between the communications of the foot to the spring pole high above, which is then read in the relative speeds and intensities by the hand pressing its material downward. The oscillations of upward and downward, a horizontal, yet fixed, stable circular whirrings do suggest a grid of complex physical actions and interface. One may be tempted to see in this cross-dynamic the metaphysics of the verticality of Substanced expression, and the horizontality of modal causations. In any case, the foot pedal lathe leaves a distinct epistemo-kinetic imprint upon the craftsman that engages it, something that surely would have informed Spinoza’s thinking about material and its formation. 

Yet on the level of information on technique, perhaps even of more interest in this close up of the Hevelius drawing is the shape of the grinding forms discs placed haphazardly on the floor. They are not the hollowed-out concave metal forms like those, let us say, Hieronymus Sirturus wrote about in his influential book on technique Telescopium, siue Ars perficiendi nouum illud Galilaei visorium instrumentum ad sydera (1618), (whose spherical perfection was created by being ground against a matching convex iron casting). They appear instead concavely beveled, on the inner slope of which a lens can be angled to be ground (if I read the illustration correctly).

One can see each of these types of grinding forms (a beveled inner edge, and the scalloped dish) in van Gutschoven’s 1663 letter to Christian Huygens which had answered Christiaan’s question as to how to grind smaller objective lenses [comments on: A Method of Grinding Small, Spherical Lenses: Spinoza ]:

Here in the van Gutschoven illustraton a narrow canal (vertically aligned) serves as the grinding surface just inside the lip.

And here is a concave finishing form, in whose center a small lens would be placed for polishing. The two illustrations above simply show that both form designs were employed, and we cannot be sure if Spinoza would have used one or the other, or both (though the degree of curvature shown above would be wholly inappropriate for telescope lenses for which only a slight curvature was needed). One might add, by Spinoza’s use of the terms “dishes” or “plates” for his metal laps, the scalloped spherical form, hollow at the center, one could presume was a main metal form that he used.

To return to the Hevelius example, if we can seriously entertained the prospect that Spinoza used a foot-pedal grinding lathe, I would want to point out the thorough and bodily engagement that grinding would have involved. Not only were the powers of close-eyed concentration, and precise fingered and armed exertions involved, but also a co-ordinated rhythm between the actions of the foot that from a distance below swiveled the grinding form back and forth, reversing itself, restrained from high above, bringing fortha total read of machine tensions which completed a lived circuit between the human body and its attentive results. Spinoza’s entire body would be in play in the workings of the glass, from head to toe. And if one superimposes the requirements of his metaphysics (his equivocal treatment of Thought and Extension, and his definitions of a body and power) upon this organization of machine, idea and flesh, one may see with growing clarity how his crafted practices informed his most abstract thinking.

This is the case found in the Hevelius example, which forms one end in the spectrum of the possible machine designs Spinoza likely used. There is of course a much simpler design, the hand-driven lathe, which Spinoza may have also worked from. The nature of this lathe can be seen in the 1660 Manzini manuscript, and the expert mock up made by the 400th Anniversary of the Telescope team:



One can see the typical concave metal dish (to the left) and the hand-drive of the form. In terms of dynamics instead of a swivel motion to the form, a repeated back and forth oscillation driven by the foot co-ordinated from high above, here the form can be spun in continuing circles in close proximity to the chest. Evidence that Spinoza used just such a design perhaps can be seen in the list of things sold from his estate in November of 1672.

and various instruments for grinding (‘en verscheidene slypgereedschap’) like mills (‘molens’, also plural!) and great and small metal dishes serving for them (‘groote en kleine metale schotels daartoe dienende’) and so on” (en so voort).

That there were multiple mills sold (not a complete list of what he owned one might assume) suggests a variety of more specialized devices, instead of one large workbench as that shown in the Hevelius example. But this is not at all a clear, or exclusive conclusion. Small hand-driven grinding lathes may have been employed for small microscope objectives (which Spinoza favored) or telescope eye-pieces, whereas a foot pedaled, spring pole machine could have been used for larger telescope glasses which could reach nearly 1/2 a foot in diameter.

In digression, there is evidence that Spinoza collaborated with the respected optical mathematician and amateur scientist Johannes Hudde on calculations for a 40 ft lens. To give a sense of it, such a lens would have been approximately 5 inches in diameter, of very slight curvature and only 5 – 8 mm thick: Huygens’s letter to his brother 23 Sept 1667:“Ie voudrois scavoir quelle grandeur d’ouuerture Spinosa et Monsieur Hudde determinent pour les 40 pieds” (See “The Lens Production of Christiaan and Constantijn Huygens” , 1998, by van Helden and van Gent, for the dimensions of similar lenses). Whether Spinoza was in the practice of grinding such lenses, which at the time would have been among the most powerful telescope lenses in Europe, we cannot know. But it seems he was involved in their calculation.

To return, if we are to imagine a hand-driven lathe’s effect upon Spinoza’s rational conception of Mind and Body relations, the form’s spinning, instead of oscillating, motion, may involve less of the entire body than a foot pedal lathe would; the head, the shoulders, the hands would form a frame of power and sensitivity, withthe shoulders acting as fulcrum points of stability and the hands as reading extensions. The cybernetic feedback between the hands, one holding the glass blank, the other whirling in circles would seem to be even more involved, more kinetically woven than that of the foot pedal lathe. The power transfer is more direct the thus the communication between hands more intimate. And one sees how the manifestations of concentric stability and change, eternity and flux, expressed in two respondent revolving discs, certainly could present itself as significant to the circle-loving craftsman as he sought to perfect his lens under physical pressure and frictions of grit.

By my view it seems most likely that Spinoza employed both kinds of lathes, the foot and the hand driven, perhaps at different points in his life, in a process of a refining of techniques. What really is at stake in this analysis I would contend is that one must be able to SEE what Spinoza did during a preponderance of his days, picture it physically, in an affective projection, to fully conceive what he thought. The machine and the human, that mind in the device and the matter of the idea understood to be in mutual conjunction.

The Rijnsburg Lathe: Like the Sun, not 200 Feet Away

Mystery Solved: Rijnsburg Lathe, a 19th Century Woodturner’s Lathe

Stan Verdult over at the excellent Spinoza site has done excellent research and unearthed the origins of the Rijnsburg lathe, which for some reason the Spinozahuis seems to have been less than forward about. He has uncovered a 1984 Bulletin which tells us that H.G. van de Sande Bakhuyzen who was at that time [±1899] director of the Leiden observatory made an inquiry into the buying of the cutting lathe from a wood turning shop (houtdraaierij) at Leiden, the name (“Dusoswa”). The device had been used for a long time and was to some degree worn out. For a time it was held in the foyer of the observatory before it was taken to Rijnsburg. Without any doubt it is a product of the nineteenth century. It appears to be in mechanical form, less like any grinding lathe Spinoza may have used, and more like a woodturners lathe, used for carving [the above description is my wide paraphrase from Stan Verdult’s most generous rough translation of a portion of the article for me].

Here is an article portion, for those that read Dutch:

I post here my response to Stan Verdult’s call that the lathe should be removed. It makes such an interesting case for those that take Spinoza’s philosophy seriously. Spinoza’s central distinction between Rational and Imaginary knowledge comes into view. The useful impression that the lathe was authentic is part of a museum’s theatrical powers, the attempt to re-create many of the associations that one would have, that Spinoza must have had when walking into that room. In a sense, the “inauthentic” lathe (IS it inauthentic?) delivers many of the affects that an empty room could not. Is this a knowledge that Spinoza would favor?

My posted comment at Stan’s site:

I loved what you have said about the lathe. This is wonderful research. And I do question why the Spinoza house has not been more forthcoming about the nature of its exhibit. But if you are recommending that the lathe be removed from the Spinozahuis in September I’m not sure that that is a good idea. First of all, the lathe gives a strong sense that Spinoza himself worked at lens-grinding. It creates an impact that is important. One should only take it out if there was another that would replace it (which may not be more authentic: perhaps if it was modeled on an image from Hevelius for instance this would be an improvement, but still it would only a guess). Secondly, the lathe there has become a bit iconic. It forms a large part of the visual memory of the house for those that have been there over the years. An empty room would not do. The big problem is that it is not properly labeled. One should simply know that this is a 19th century woodturner’s lathe, just meant to give a general idea, an impression. Lathes in the 19th century had not progressed much from the lathes of the 17th century, and it seems likely that Spinoza used a lathe that was fairly simple in design. (The semi-automatizing “improvements” of savants like Christiaan Huygens were not necessarily seen as improvements by Spinoza: see Letter 32). The odd thing is that the story you have uncovered is a fascinating one. It reveals the texture of the Spinozahuis itself, its living history, the way that history is made. A museum simply does not exist “sub specie aeternitatis”. Revealing how the lathe got there, and acknowledging its role in the living history of the museum would actually direct our attention to some of the more important features about a house trying to keep the memory of Spinoza alive, that history is an effort and a narrative. The important thing is for the exhibit to be clear, and when it is not clear, accurate, I would think.

With the 400 year anniversary of the telescope coming to Middelburg in September, this would be a natural time to emphasize the Spinozahuis lathe’s history, and to organize additional information around the piece letting others become more aware of Spinoza’s commitments to optics, not a small portion of his life.

Spinoza writes of the sun, “when we look at the sun, we imagine it as about 200 feet away from us, an error that does not consist simply in this imagining, but in fact that while we imagine it in this way, we are ignorant of its true distance and the cause of this imagining. For even if we come to know that it is more than 600 diameters of the earth away from us, we nevertheless imagine it is near. For we imagine the sun so near not because we do not know its true distance, but because an affection of the body involves the essence of the sun insofar as our body is affected by the sun” (E2p35s).

The Spinozahuis imaginary presentation of a lathe in a taken-to-be authentic environment provides an interesting case of the theater of the past. We want to affectively feel what the past was like, and part of feeling that is knowing the facts of the past. Though our affective affinities the Spinozahuis lathe communicates many of those facts in a most imaginary way, the wood in its size and geometery speaks to us, and this is important. But if we are to be freed, in a Spinoza sense, our affects must be coupled with knowledge, the tracing out of that tenuous line to the past, one that might mitigate from moment to moment our imaginary composition, but will not diminish it altogether. The sun will still appear to be 200 ft away, and the sun will still rise up out of the sea, even though we know that it does not. But we will be free to know why it does these things.

Glazemaker’s translation of Descartes’ La Dioptrique (1659)

Being blind to Dutch, Stan Verdult over at, was so kind to point out that of the listings of Glazemaker’s translations below, one of them is of the germane La Dioptrique, by Descartes. This is published two years before Spinoza left Amsterdam, 1659, by Timon Houbaak, (if I read correctly).

The significance of this is that this is likely the text that Spinoza (and Jelles) would know and have some reference to as to the questions of letters 39 and 40. It shows an abject familiarity with Descartes’ optical theories by Glazemaker, who as part of the Rieuwertsz/Van den Enden circle would have brought them to bear. In terms of timing and content, there is a useful co-incidence of Glazemaker’s potential glass knowledge and Spinoza’s lens-grinding and Descartes’ La Dioptrique. Here is the link to the book: Descartes, Proeven der wijsbegeerte (1659). We have not established a strong Glazemaker and Spinoza connection at this point, but there is at least the suggestion.