VOL. XXXII.] PHILOSOPHICAL TRANSACTIONS. ' 5Q3 



of tables by differences. It consists of 10 propositions, most admirably con- 

 trived for expeditious computation of intermediate terms in any given series. 

 The last proposition, which contains a general solution of the whole design, 

 is this, datis seriei cujuscunque terminis aliquot aequidistantibus, quorum inter- 

 valla secanda sunt in sequales quotlibetcunq ; partes, propositum sit invenire 

 terminos interserendos. 



The book concludes with three small tracts, concerning the descent of bodies, 

 the motion of pendulums in the cycloid, and the motion of projectiles, com- 

 posed in a very natural and easy manner. 



The author has written some other pieces, yet unpublished, which the editor 

 has given an account of in his preface to the book. 



Observations on a Foetus^ and the Parts of Generation of a Sheep. By Mr. 

 Leuwenhoeck, F.R.S, N°373, p. 151. 



A ewe, which within 2 years had twice lambed, happened to be covered by a 

 young ram, about 20 weeks old; about 5 days after the ewe was killed, and 

 out of her belly was cut 28 lb. of fat. But observing, on opening her, that 

 the uterus was four times larger than ordinary, the butcher brought it, with 

 the ovaria, to Mr. L. assuring him, that it was not yet quite 5 days since the 

 young ram had covered the sheep, and that there was no other ram there- 

 abouts. 



Mr. L. began first to try to penetrate into the uterus from the vagina, with 

 the point of a small pair of scissars; but found it so close that he could not; 

 he therefore cut a piece off from the uterus, out of which ran a clear water, 

 and within it lay the foetus with all its coverings. Spreading this on the back- 

 side of a China tea-dish, and finding that it still contained more water, he 

 made a small incision to drain it, and to let it dry, to observe it the better. He 

 could plainly see the vertebrae of the neck and back, as also the joints of its 

 short tail; he thought likewise that he saw the eyes. But when it was quite 

 dry, he could not observe its backbone so well as before, when it was as yet 

 moist, though the painter, who made the draught, and had sharper and younger 

 eyes, saw the bones of the back very distinctly. The design in drying it, was 

 to cut it in small slices, the better to observe the inner parts: for it was so 

 extremely soft and tender when moist, that with the least touch its parts would 

 be disordered and confounded. He therefore cut the foetus into 15 slices, and 

 observed them with a microscope, but could not be very certain about what he 

 saw; though he imagined he saw the intestines, the bladder, and the heart; 

 but he saw and observed, with a great deal of pleasure, that two blood-vessels 

 lay near together in the brain, and how they were spread into branches. 



VOL. VI. 4 G 



