282 Mr Tregaskis on the Elastic force of Vapour. 



Art. XIII. — Notice on the Elastic Fcyrce of Vapour. By Ri- 

 chard Tregaskis, Esq. Communicated by the Author. 



The freezing point being zero, call the temperature and the 

 force at any given distance above it — unity. Raise the tem- 

 perature from that point, till the force be doubled, and it will be 

 found that Jth only is added to the temperature. Here the 

 temperature is IJth; the force 2. And hence l|th, or 1.2 

 (not 14 reduced to 1.2, as printed on page 69 of the last Num- 

 ber,) is the ratio of temperature, 2 the ratio of force. 



That this law continues in operation from 15 to 240 inches 

 of mercury, appears from the following table :- — 



« 



The force of steam at various temperatures in inches of 

 mercury. 



By Experiment. By Calculation. 



Abov6 



Fahr. Inches. Freezing. ^^^^^' Inches. 



^^^ JL« ^T"''°""'l 150» 182° IS 



15.86 Dalton, J 



212 30 Atmospheric pressure, 180 212 30 



248.5 60.40 Ure, - 216 248 60 



Ifa Jo^-^^ ?'':, 1 259.2 291.2 120 



293 120 Southern, J 



343.6 240 Southern, - 311.04 343.04 240 

 The experiments in Article X. of the last Number did not 



appear on the same page with the calculation. This circum- 

 stance, which made the comparison difficult, together with an 

 error of the press noticed above, which rendered that part of 

 the article obscure, will, it is hoped, be accepted as an apo- 

 logy for introducing the subject again. 



Art. XIV. — Descriptionqf some remarJcahle Nebulce and Clus- 

 ters of Stars in the Southern Hemisphere, observed at Pa- 

 ramatta in New South Wales.* By James Dunlop, Esq. 



The following nebulae and clusters of stars in the southern 

 hemisphere were observed by me. at my house in Paramatta, 



• This is an abstract of Mr Dunlop's large and valuable Catalogue 

 published in the Fhil Trans, 1828, p. 113. It is illustrated by seven 

 large Plates, which it is impossible to copy into a Journal. 



