.VOL. XI.] .PHILOSOPHICAL TRANSACTIONS. 343 



that they found them succeed as I had affirmed. And therefore since Mr. 

 Lucas has found the same success, I suppose that when he expressed that he 

 mucli rejoiced to see the trials of the Royal Society agree so exactly with his, he 

 meant only so far as his agreed with mine. 



And because I am again upon this first experiment, I shall desire that Mr. 

 Lucas will repeat it with all the exactness and caution that may be, regard being 

 had to the information about it, set down in this letter; and then I desire to 

 have the length and breadth of the image with its distance from the prism, set 

 down exactly in feet and inches, and parts of an inch, that I may have an op- 

 portunity to consider what relation its length and breadth have to the sun's dia- 

 meter. For I know that Mr. Lucas's observation cannot hold, where the re- 

 fracting angle of the prism is full 6o degrees, and the day is clear, and the full 

 length of the colours is measured, and the breadth of the image answers to the 

 sun's diameter : and seeing I am well assured of the truth and exactness of my 

 own observations, I shall be unwilling to be diverted by any other experiments, 

 from having a fair end made of this in the first place. Sir, I am, &c. 



Postscript. — I had like to have forgotten to advise, that the experimentum 

 crucis, and such others as shall be made for knowing the nature of colours, be 

 made with prisms which refract so much, as to make the length of the image 

 five times its breadth, and rather more than less ; for otherwise experiments 

 will not succeed so plainly with others as they have done with me. 



An Account of two Books. N° 128, p. 705. 



I. Tractatus de Ventriculo et Intestinis, cui praemittitur alius de Partibus 

 Continentibus in genere, et in specie de Partibus Abdominis ; Auth. Franc. 

 Glissonio, M. D. et Coll. Med. Lond. Socio, nee non Soc. Regalis College. 

 Lond. 1676, 4to. 



In this treatise Dr. Glisson reasons largely concerning the nature of the 

 muscular fibre, irritability, the peristaltic motion of the intestinal canal, di- 

 gestion, &c. &c. 



n. Pharmacopee Royale, Galenique et Chymique, par Moyse Charas, Apo- 

 ticaire Artiste du Roy en son Jardin Royal des Plantes. A Paris, 1676, 4to. 



This pharmacopaeia was once in great repute, but is now quite obsolete. 



Observations on some considerable Parts of Asia. By M. Tavemier. N° 129, 



p. 711. 



Ispahan is about the size of Paris; but Paris has ten times more people than 

 Ispahan. The air of Gomron, a seaport town in Persia, from April to Novem- 



