Appendix: Burchard de Volder’s Experimenta philosophica naturalia (1676–1677) [78r] Experimenta philosophica naturalia, auctore M[a]gis[tro] De Valdo Lugd[uni] ann[o] 1676.1 1um 12 Martii His subject was the ponderosity, or rather the compression of the air over us, which he had proved by some other experiments before now. Yet to assert it more authentically, and to give the auditory to understand that it was not the metus vacuii2 which did make nature to work so violently, and potent in many operations, but rather the compression of the air itself, he used the following demonstration. First he had made two little cylinders of white stone perfectly round, and perfectly plane on the superficies, where they were to touch one [78v] another, and as perfectly equal to each other as he could get them made. Their diameter was <about> \just/ two inches and ⅓d each, and the depth, <mi> or length, might be a little more Next he joined these two cylinders together with a little tallow, and no other artifice, and so close that not the least atom of air could get in betwixt them: and this he said he did least any might calumniat3 that the superficies were not perfectly plain and conse- quently some air must be got in betwixt them, for at least, quoth he, those very little 1 Conventions adopted in the transcription: (1) the text deleted in the manuscript has been put between brackets thus < >; whenever possible, I have provided the deleted text; otherwise, I have used dots instead of the illegible letters; (2) the text in the margin or between the lines is put between the symbols \ /; (3) doubtful text is put between brackets { }; whenever possible, I have provided the text, otherwise, I have used dots instead of the illegible letters; (4) my additions are put between brackets [ ]; (5) the text has been modernized, i.e. forms like “y.e” have been rendered as “the”, plurals given in the form “cylinder’s” have been rendered as “cylinders”, the ligatures have been dissolved, obsolete and archaic spellings and forms of words have been rendered into modern terms, punctuation has been fixed. Latin has been translated in footnotes, whenever neces- sary, and Latin abbreviations have been completed. Doubtful text has been kept in its original form. 2 “Fear of vacuum.” 3 “Calumniate.” © Springer Nature Switzerland AG 2019 619 A. Strazzoni, Burchard de Volder and the Age of the Scientific Revolution, Studies in History and Philosophy of Science 51, https://doi.org/10.1007/978-3-030-19878-7 620 Appendix: Burchard de Volder’s Experimenta philosophica naturalia (1676–1677) Fig. 1 Cohering marbles used by De Volder. (Source: De Volder 1676–1677, 78v. Courtesy British Library, ms. Sloane 1292) holes which might be left by the unevenness of the superficies, are closely staying with the tallow. 3ly. He hung them up (for which purpose they had brass hooks at both ends thus [see Fig. 1, De Volder 1676–1677, 78v]) [79r] Then he put weights to the lowermost end, which was first a huge scale weighing 35 lb with all its {tanr’}, and then into the scale he went adding by degrees more and more weight: to the intent he might experiment how much weight would tore those two cylinders asunder, which were only joined with a little tallow. Has he added to the weight of 285 lb, and then the lower brass hook of the cylinders broke, which had it not happened it would in all probability have sustained much more weight. This experiment he said did prove the compression of the air, and its ponderosity of whose nature it is as in fluid bodies that it weigheth and compresseth both above us, and beneath us: where by the oppression of the air upon the uppermost cylinder meeting with the oppression of the air, or heaving under the lowermost \{uider fa}/ did cause that reluctancy to a disunion of the cylinders: here being no air drawn out, nor left in, not the least, between [79v] the two cylinders, which might be said to be the cause of their own separation propter metum vacuii4 which is the common solu- tion of Aristotelians for such reluctances in such cases.5 [80r] Experim[en]tum 2um 13 Martii. His subject was the same viz. the pressure or ponderosity of the air. 1. For this purpose he had refitted again his cylinders with better hooks (the just breadth of said cylinders being 2 digitos cum 3a parte,6 as he declared again more expressly this day), and joined them together with tallow two days before very close by means of the heat of a lamp, or candle, which joining, after the divulsion of the 4 “Because of the fear of vacuum.” 5 See Schott 1657, 25–26. 6 “Two inches and ⅓.” Appendix: Burchard de Volder’s Experimenta philosophica naturalia (1676–1677) 621 cylinders, appeared to be so thin, or superficial as that are scarce could perceive any tallow upon the superficies of one of the cylinders, which I had in my hand. 2. Then he hang them up, as before, and into the scales he added more, et more weight, till they disunited and the one fell down with the weight which appeared to be very nigh 450 lb. [80v] 3. He said Boyle could only hang on two such cylinders (being even some- thing broader i.e. of 3 fingers breadth) 80 lb weight, which is not the 4th part of this experiment. Let this he attributed to the unevenness of the cylinders of Boyle, and partly to this gluten which was only a certain oil.7 4. His conclusion was the above-said viz. that the compression of the air, both from above, et below, as being a fluid body like unto water, did hinder their separa- tion, et there not being the least jot of air betwixt them, whereby the compression of the air being equal on both sides must needs equally force, and compress, on cylin- der against the other, just as when two weights of equal ponderosity do compress two boards they cannot be separa- [81r] ted till the force, which is to separate them, be stronger than the weights: but if any thing were betwixt the two boards which might press on one side, or other, or both together, then certainly the separating force need be much lesser. 5. Hence he explicated the compression of the air to be like the compression of the water, which is not felt when we are in a river, or sea, be cause all the water compresseth equally on all sides: but were there in the bottom of the sea a tubulus,8 hole, or cavity, which had not one drop of water in it, we should feel all the weight of the water then to press, and ponder, upon us, and with huge violence to force us into that hole, whereas were the hole full of water we should feel no such violence forcing us into it: even so the air.9 6. Hence [81v] also he inferred, as above that it was not the metus vacui which did hinder the separation of the cylinders with this dilemma: aut non datur talis metus vacui, et coë[u]nt illa, talis metu,10 cum non detur, nequit impedire avulsio- nem cylindrorum. Aut si datur, et ille sit qui impediat disiunctos, iam profecto disi- unximus illos, et coë[u]ntes datur via, et modus, introducendi vacuii in na[tur]am: imo fecimus ipsi mo[do] vacuum, q[uo]d utrumq[ue] negare de[be]nt, qui vacuum tantopere abohrrere na[tur]am aiunt.11 7 See Boyle 1662a, 84–86. 8 A small tube. 9 See Stevin 1605, 148–149; AT II, 587–588; Boyle 1666, 231–232 and 242, 1999–2000, volume 7, 220–221. 10 Sic. 11 “Either this fear of vacuum does not exist, and those [cylinders] cohere, [but] since that fear does not exist, it cannot impede the separation of the cylinders. Or, if it exists, and that is what hinders that they [are] separated, [and] we actually have already separated them, since they [were] coher- ing, it is given a way and manner to introduce a vacuum in nature: what is more, we created a vacuum in this very way[.] Those who say that nature abhors a vacuum to such an extent, have to negate both [these alternatives].” 622 Appendix: Burchard de Volder’s Experimenta philosophica naturalia (1676–1677) 7. By the way he explicated the opinion of Descartes, which holdeth that all the cohesion or union, of bodies, proceededh only from their quies.12 But unto this he said he could not assent. For certainly quoth [82r] he if this quies be so strong that I have not force to separate two things, how comes it that I can so easily move the whole v.g. a whole iron, or board, which with my hands I cannot tore in pieces, yet I can rowle it to and fro? Or if I cannot separate the half, 3rd or 4th part of said things yet I may at least separate the 100 or 1000th part of them, the force of my hands and their bigness being so much bigger than said 100 or 1000th part. 8. Unto this Descartes answereth that the softness of our hands the pain we feel and our only touching said things s[ecun]dum extimam superficiem13 is the cause we cannot separate not so much as the least part of many solid things.14 9.