Adams Papers

[April 1754]


[Winthrop’s Lectures on Experimental Philosophy.] April 1st. 1754.1

Mr. Winthrop began a series of Experimental Phylosophy2, and in the 1st place he explained to us the meaning, nature, and excellence of natural phylosophy, which is, (he says) the knowledge of those laws by which all the Bodys, in the universe are restrained, it being evident that not only those great masses of matter the heavenly Bodys, but all the minutest combinations of matter in each of them are regulated by the same general laws. For instance it is plain that all the planets observe exactly the same uniform rules in their revolutions round the sun, that every particle of matter observes on the surface of the earth.—As to the usefulness of natural phylosophy, to be convinced of that, it is necessary only to reflect on the state of all the Civilized nations of Europe, compared to many nations, in affrica, of as quick natural parts as Europeans, who live in a manner very little superiour to the Brutes.—The first Cause, and indeed the alpha and omega of natural phaenomena, is motion, their being an utter impossibility that any effect should be produced in a natural way without motion, and <this motion or rather Bodys in motion are subject to the following laws, 1st two bodys of different velocitys or swiftnesses, but aequal masses> which motion is subject to Certain laws which he ex­plained, and I have forgot. But thus much I remember, that motion, produced by gravity, was universally in right lines, from the body acted upon by gravity, to the Center of gravity, as the Center of the earth, for instance, or the like. He explained also, powers, weights, the line of direction of powers and weights, the Center of gravity, Center of {10} magnitude, and Center of motion, with the several methods of finding them, some of which I’ve forgot, and the rest he showed us examples of which cant easyly be exhibited. But by reason of some of these laws (he tells us) there are two famous towers in Italy, the one at Bolognia, and the other at [Pisa]3, each near an hundred feet high which are not in a perpendicular position, but inclined to the horizon to a Certain degree, so as not to have the line of direction fall without the Base, because if the line of direction fell not within the Base, the buildings would inevitably fall. After this and many other things and Terms relating to motion, velocity &c. explained he dismiss’d us for the first time.—He touch’d also upon the advantages of gunpowder in war, above those of the Battering ram. For says he, the Battering ram was a hugh,4 and unweildy peice of timber or rather combination of timbers, with an iron head much in the shape of a rams head, whence it drew its name, commonly weighing near forty thousand Pounds, and consequently required a 1000 men to manage it, a man being scarce able to handle more than 40 lb. with velocity enough to do execution. Now one of our cannon, by the almost irresistable force of rarifyed vapour will discharge a 36 pounder so as to make as large a Breach in a wall, as the Battering ram, and requires but <about 6> 5 or 6 men to order and direct it. Therefore 6 men can do as much execution now with a Cannon as 1000 could with a Battering ram, and the momenta are equal the velocity of the Cannon exceeding {11} that of the ram, as much as the ram exceeds the Cannon in weight, that is as 36:40000.

1This is the true beginning of JA’s notes on Professor John Winthrop’s lectures; he had first started them two pages earlier in the MS and then canceled that beginning for reasons explained in the note there (p. 55, above); see also note on entry of 19 March 1754, above.

All the notes on Winthrop, which continue through 11 April, are in JA’s variant or experimental hand of 1754–early 1756, discussed in the Introduction.

2The “Course” or series of lectures on Experimental Philosophy was required by the terms of the Hollis professorship to be given at least once a year. Designated “private lectures,” they were intended only for the sophisters (Endowment Funds of Harvard University, Cambridge, 1948, p. 55–56; Morison, Three Centuries of Harvard description begins Samuel Eliot Morison, Three Centuries of Harvard, 1636–1936, Cambridge, 1936. description ends , p. 80). The terminal dates of a course of lectures such as this did not coincide with term times but rather with the period between March and the end of June when senior sophisters were required to be in Cambridge; see note on entry of 29 June 1753.

The notes taken by JA on the lectures indicate that the course as begun in 1754 was to be essentially the same as the thirty-three lectures prepared by Professor Winthrop for delivery one to five times a week (ordinarily three), from 10 March to 16 June 1746, a lecture-by-lecture summary of which in Winthrop’s hand, with additions for 1747, is preserved in MH-Ar: “The Summary of a Course Of Experimental Philosophical Lectures, by Mr. J. Winthrop.” A facsimile of Winthrop’s outline of the first lecture is reproduced as an illustration in the present volume.

3Editorially supplied for a careless omission in MS. Winthrop’s “Summary” does not mention the towers.

4Thus in MS.

April 3d. 1754.

The second lecture, which was wholly taken up in explaining the Propertys of the Centers of gravity and motion, which were applyed to the instruments, Cheifly in use in Common life, such as, the lever, pulley, Ballance axis in peritrocheo,1 &c. But the Ballance was principally insisted on. The reason of it was fully explained and the method of weighing, viz the distances of the Bodys from the Center of motion, must be precisely in a reciprocall proportion of their quantitys of matter or weights, always alowing for the weight of the Beam on which they are suspended, as well as friction, and the falsity of the supposition, that radii proceeding from the center of the earth are parrellel. Mr. Winthrop also demonstrated to us that all the advantages arising from any of the engines in use, resulted from the different possion [position] of them, with relation to force and velocity, thence he shew’d the famous problem of Archimedes viz, to move any weight however great by any force however small.—I had like to have forgot that he applied the doctrines of the center of gravity to the heavenly Bodys, shewing us the affections of the sun and planets with respect to their Centers of gravity, and instructed us in the manner of finding the Common Center of gravity of any 2 of ’em e.g. earth and moon, viz By this proportion as the quantitys of matter in Both added together is to the quantity of matter in the one separtely so is the distance of their centers to the distance of the Center of the other, from the Common Center sought. And to find the common Center of gravity of 3, 4 or 5 or any given number of Bodys, having found the common center of any 2, from that said Center draw a line to another of said Bodys and find the common Center of gravity of these two respecting the {12} common Center of gravity of the former 2 as a Body containing a quantity of matter equal to Both said Bodys.

1See OED description begins The Oxford English Dictionary, Oxford, 1933; 12 vols. and supplement. description ends under Peritrochium, quoting John Harris, Lexicon Technicum (1704): “The use of this Peritrochium is to make the Cylinder or Axis be turned the more easily by the means of Staves or Levers, which are fix’d in its Circumference.” See also Thomas Jefferson’s Notes of a Tour through Holland and the Rhine Valley in 1788:

“A machine for drawing light empty boats over a dam at Amsterdam. It is an Axis in peritrochio fixed on the dam. From the dam each way is a sloping stage. The boat is presented to this, the rope of the axis made fast to it, and it is drawn up. The water [on one] side of the dam is about 4.f. higher than on the other” (Jefferson, Papers, ed. Boyd description begins The Papers of Thomas Jefferson, ed. Julian P. Boyd and others, Princeton, 1950– . description ends , 13:9).

Evidently Winthrop dealt in more detail with this mechanical device in a later lecture; see entry of 6 April, below.

April 5th. 1754.

The theory of the Ballance, scales, steel-yard &c. <and all> and the 3 species of lever’s continued to which (viz) the lever he referred allmost all the instruments in life, and universally. To make a aequilibrium, the product of the quantity of matter in the weight multiplyed into its distance from the Center of motion, must be equal to the quantity of matter in the power, multiplyed into it’s distance from said Center.

April 6th. 1754.

<The phaenomina of> The nature of the Pulley, axis in peritrochaeo, and inclined Plane explained, which all depend on the laws before laid down (viz) that the quantity of matter in the weight bears the same proportion to the quantity of matter in the power, as the distance of the power from the Center of motion, to the distance of the weight from said Center.

April 8th. 1754.

The Theory of simple machines and in particular of the inclined plane, of the wedge and screw, and other machines compounded of these simple ones, finish’d.

April 9 1754.

Sir Isaac Newtons three laws of nature proved and illustrated, together with the application of them to the planets, which are kept in their orbits by two forces acting upon them, viz that of gravity and that which is call’d their Centrifugal force whereby <it> they strives to recede from the Center of their orbits, and fly off therefrom in tangents.


April 10, 1754.

The theory of Centrifugal forces, continued; and aplyed to the Cases of the planets; and from this Centrifugal force, Mr. Winthrop confuted the hypothesis of vortices, from this also arises the spheroidal form of the earth.

April 11 1754.1

Some thing’s observed concerning gravity, which encreases as you approach the Center of the earth in a reciprocal proportion of the squares of the distances, and under this head were introduced pendula and we saw that all pendula of equall length oscilated in equal time whether the arches they described were greater or less. We were also inform’d that bodys falling in Chords of a Circle will fall in equal times Caeteris paribus; and in the same time that the same Body would pass through the diameter, as

1JA’s notes on Winthrop’s course of lectures end with this entry, for the very good reason that Winthrop broke off his course this year with the eighth lecture in order to travel to Philadelphia, where he met his fellow scientist and correspondent Benjamin Franklin for the first time. His trip kept him away from Cambridge from 15 April to 24 May. See his MS Diary for 1754 (MH-Ar); also Sibley-Shipton, Harvard Graduates, description begins John Langdon Sibley and Clifford K. Shipton, Biographical Sketches of Graduates of Harvard University, in Cambridge, Massachusetts, Cambridge and Boston, 1873– . description ends 9:246–247.

The present entry also ends JA’s efforts (so far as we know) to keep a diary as a Harvard student, although he was not graduated until July 1755. As explained in the Introduction, an interval of more than four years passed before he made further use of the folio MS designated as the Diary Fragment. When, in Oct. 1758, he did so—having already begun in Nov. 1755 a diary record in pocket form—he used the MS for different and very miscellaneous purposes rather than as, strictly speaking, a diary; see the following entries.

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