Chemical Instruments and Operations. 293 



is demonstrable, a priori, and is proved by an abundance of 

 historical facts. That vapor is a powerful conductor, is 

 proved by the multitude of cases of persons struck standing 

 at doors and windows at the approach of a thunder gust. 

 The mist thus ascending, rises to the upper regions of the 

 atmosphere, and then spreads itself, accompanied by the 

 electric fluid, which causes those wonderful displays that 

 baffle description, and exceed the power of imagination. 

 It is not incumbent on me, but foreign to my subject, to ex- 

 plain what becomes of that portion of electricity that goes 

 southerly ; but it is not irrational to conjecture, that it may 

 be one of the causes that produce those extensive earth- 

 quakes, that have traversed the ocean and have been felt in 

 different parts of the globe. This theory also accounts for, 

 and derives strength from the fact of the detachment of 

 those immense masses of ice from the polar regions ; no 

 philosophical reason or adequate cause, has been or can be 

 assigned, for this singular and wonderful fact except electri- 

 city. No other cause that we are acquainted with, is suffi- 

 ciently powerful to separate those frost bound masses and 

 set them afloat. It is a well known fact, that those floating- 

 continents of ice are much larger, at some periods, than at 

 others ; and that they have greatly increased within the pe- 

 riod that the northern hghts have been observed to increase, 

 is certainly true ; but to decide whether the former have fol- 

 lowed so soon as to be coupled as cause and eflfect, requires a 

 knowledge of facts beyond my observation and research. 

 Many facts in confirmation of these views, might indeed be 

 added, but they v^^ould introduce other subjects vastly more 

 important, which I am not prepared now to discuss : and 

 perhaps enough has been offered to determine whether the 

 discussion is worth pursuing. S. 



Whitesborough, Oneida county, N. Y. Feb. 16, 1829. 



Art. XV. — Chemical Instruments and Operations; hy Rob- 

 ert Hare, M. D. Professor of Chemistry in the University 

 of Pennsylvania. 



A modification of the process for ascertaining the specific 

 gravitij of the gases. 



The principal difficulty in weighing the gases accurately, 

 arises from the small proportion which the weight of any 



