330 PHILOSOPHICAL TRANSACTIONS. [aNNO l66g. 



universal wherever the point be assigned, from vi^hich the shortest lines are to be 

 drawn ; which he has extended and applied to those infinite sorts of other para- 

 bolas. — Chap. 7 treats of the dimension of figures from the given centre of 

 gravity. This he says is accurately handled by the learned already; yet he adds 

 some easy methods of his own, which may be applied to good use ; for, in any 

 cui-ve, if there be ordinates enough given, standing erect at an equal parallel 

 distance, you may approach the area, and if by aid thereof you find the centre 

 of gravity, then do you obtain the measure, either of the round solid or spindle 

 made by the rotation of the given figure, or of hoofs raised upon it as a base. 



Chap. 8. The author shows an easy way of finding the centre of gravity of an 

 hyperbolical conoid, and that in order to the resolution of this problem : To 

 find the locus in which are all the centres of hyperbolic conoids, which are 

 generated from hyperbolas cut in a given right cone, and having their axes 

 parallel to that of the cone; which he finds to be an hyperbola. — Chap. Q 

 treats of the centre of gravity of the lunula of Hippocrates of Chios ; and shows 

 that if Hippocrates had given that, as he did the quadrature of the lunula, he 

 had squared the circle. — Chap. 10 treats of arithmetical problems ; wherein he 

 asserts that Diophantus was wont to solve arithmetical questions with great sub- 

 tilty, but uses numbers only ; whereas the same may often be more easily and 

 universally solved by algebra : of which he gives some examples. 



II. Tractatus de Corde; item de Motu et Colore Sanguinis, A. Richardo 

 Lower,* M.D.F.R.S. 



The learned author of this treatise, considering how important it was for the 

 attaining of a full knowledge of the nature and qualities of the blood, to investi- 

 gate, not only its circular motion, the origin and celerity of that motion, and 

 the various changes thereof, together with their causes ; but also to make an 

 estimate of the quantity of that liquor emitted at every pulsation ; thought it 

 very well worth while to give, from his own excellent observations, a clear and 

 particular account of the whole of this subject. And forasmuch as he conceives 

 that the motion of the blood depends on that of the heart, he begins with a 

 discourse concerning the situation and structure of the heart, to show how 

 exactly these two are calculated for its motion, and how well adapted to distri- 

 bute the blood into the parts of the whole body. 



In chap. 1 he considers the diversity of the situation of the heart in different 

 animals, and the reason thereof; proceeding to discourse of the pericardium 

 and its use, together with the origin and use of the serum therein ; and why in 

 man only that case of the heart grows to the midriff\, and what makes it to do 



* A biographical notice of this celebrated anatomist has been given at p. 197 of tliis volume. 



