104 Mr Ritchie's Observations on Leslie's Photometer. 



led to a somewhat different conclusion, by circumstances upon 

 which I rely with confidence. I subjoin a table expressive of 

 them, within a certain range of pressure. The density is 

 given only to one decimal, because I would not affect greater 

 accuracy than the present state of my investigations entitle 

 me to do. I indulge the hope of soon laying before you a 

 connected view of the habitude of an aeriform body with re- 

 spect to heat, in all circumstances. A particularization of the 

 analysis contained in the 12th Book of the Mccanique Celeste, 

 leads us immediately to refer the relations betwixt the elastic 

 force, temperature, density, specific attraction for heat, &c. to 

 the experimental determination of one constant quantity, cha- 

 racteristic of the nature of the substance under discussion. 



I am, Sir, 



Your very obedient servant, 

 22d February 1825. 



Art. XXI. — Additional Observations on Leslie's Photome- 

 ter, §c. By "William Ritchie, A. M. Rector of the Aca- 

 demy at Tain. In a Letter to Db Brewster. 



Dear Sir, 



In the last number of your Journal you remark, in a note to 

 my paper, on Leslie's Photometer, that an opinion of mine is in 



