2,^S O71 th& Specijic Gravity of the Coals 



berland, Mr. Croftliwaite obfervcd none lower than aycxs 

 feet, and none hiclier than 3150, in the courfe oF fevtraJ 

 years *. But this country being mountainous, ihey are pro- 

 bably lower than in others under the fame parallel, Lam- 

 bert, in Berlin, latitude 52" 32', in the monih of Julv 17737 

 found their height 7792 feet; thermometer 65'', and the ba- 

 rometer fnnewhat below its mean height t- Sciuickburch 

 alio remarks that clouds frequently red below the fuminit 

 of Saleve, whofe height is 2S31 feet. I'hil. Tranf. 1777, 

 p. 530 ; and Gentil, at Pondicherry, latitude 12*^, obferved 

 fome at the height of 10240 feet, ii Voy. p. 79. 



The weight of clouds Saulfure ellimates at one-third or 

 one-fourth of that of the cubic foot of air in which they fub- 

 fift. Hygrometer, p. 270. When the barometer rifes, clouds 

 are partly diifolved, as denfe air is a better iolvent than rarer 

 air, and partly rife higher in confequencc of the increafed 

 fpecific gravity of the inferior air; when the barometer falls, 

 the contrary takes place. 



XL. Report, read he/ore the Conference of Mines, on the 

 Specific Gravity of the Coals of fever a I Afines of France', 

 and on the Difference in the incrcafe of Volume tchich tbty 

 acquire hy HumeSiation. By C. Bla VIER, Engineer X' 



X HE conference of mines had long been fenfiblc of tfre 

 iieccflity of determining, with rigorous precifion, the fpccitiic 

 gravity of coals in maffcs or in large fragments, in order that 

 it might be compared with that of the fame article as fold by 

 the coal merchants. 'I'hi> obje6l was at the fame time of 

 more importance, as it would make known \yhat difference 

 humc6fation would produce on the volume which coals oc- 

 cupy in their (tate of drvnefs. 



C. Duhamel and Blavier propofed to accomplifh this 

 objcft in the execution of a labour with which they were 

 charged, in order to confirm the different affertions already 

 edabliflied by one of them, in a memoir delivered to the 

 conference on the i2th Pluviofe, year 7. 



Thefe connniffioncrs wiflied to take as a fixcdand invariable 

 bafc, the yo/it/ coal, or I'uc h as it is when exlra6fcd from the 

 Inine, that they might afterwards proceed progreflively to 

 tliat reduced to different degrees of attenuation, and parlicu- 



' lJ'AlKin\ M-eico!oltigical (ybftrvaiiGns, p. 41. 



+ Mtm. Berlin i 773, p. 44. 



;J Fi(>tn the Jo/tnal ties Mines, No. 65. — We have inftrted this paper 

 kf u ir.iy I'litnilli iil.uul liints fur fimilar experinitnts on the viritties of 

 Mill in BiiuiD; v>Uicii arc (q r.timerous. 



larly 



