148 PHILOSOPHICAL TRANSACTIONS, [anNO 1745. 



Tn Air In Water Specif. 

 Grav. 

 Water 1000 



Grains Grains 



N° 1. A Brazil Diamond, fine water, rough coat 92.425 66.\6 3518 



/ 2. A Brazil Diamond, fine water, rough coat 88.21 63.16 3521 



3. Ditto, fine bright coat 10.0'-'5 7.170 351 1 



4. Ditto, fine bright coat 9.560 6.830 3501 



5. An East India Diamond, pale blue 26.485 18.945 3512 



6. Ditto, bright yellow 23.33 l6.71 3524 



7. Ditto, very fine water, bright coat 20.66 14.8 3525 



8. Ditto, very bad water, honeycomb coat 20,38 14.59 3519 



9. Ditto, very hard bluish cast 22.5 l6.1 3515 



10. Ditto, very soft, good water 22.615 l6.2 3525 



11. Ditto, a large red foul in it 25.48 18.23 3514 



12. Ditto, soft bad water 29.525 21.140 3521 



13. Ditto, soft brown coat 26.535 18.99 35l6 



14. Ditto, very deep green coat 25.25 18.08 3521 



The mean specific gravity of the Brazil diamonds appears to be 3513 



The mean of the East-India diamonds 3519 



The mean of both 3517 



Concerning the Natural Heat of Animals. By Cromwell Mortimer, M.D., 



Sec. R. S. N" 476, p. 473. 



Since the coinplete and full demonstration of the circulation of the blood in 

 animals by our illustrious countryman. Dr. Harvey, the generality of medical 

 writers have attributed the natural heat of animals to the motion of the blood in 

 the blood vessels, or rather to an attrition of all the fluids in the animal arising 

 from it ; which fluids, from the later discoveries by injections and microscopes, 

 are found to move in conical canals communicating one with another near the 

 apices, or where the arteries are the narrowest, soon afterwards growing wider 

 and wider, when the same continued canals obtain the name of veins, and con- 

 vey back the fluids they contain to the heart. They ascribe heat in an animal to 

 strong and frequent contractions of the heart and arteries : which heat will be the 

 greater, the more dense the humours are, the more strongly they are propelled, 

 and the greater the resistances are, near the ends of the arteries. From this sup- 

 position they conclude, that the heat arises from attrition ; that, by a violent 

 agitation of the particles of the blood and humours against one another, and es- 

 pecially by their attrition against the sides of the containing blood vessels, there 

 must be great friction excited, and from that friction heat generated ; as is easily 

 done by rubbing two pieces of wood together, or a piece of wood and a piece of 

 metal, or two pieces of metal, or hard stones : but it is known, by daily experi- 

 ence, that either any watery fluid, or oily or greasy substance, applied to these 

 bodies while rubbed, will prevent the excitation of heat ; as for instance, the use 



