280 Dr. Hare's Improved Barometer Gage Eudiometer. 



Agreeably to the late investigations of the celebrated Faraday, 

 equal quantities of the electric fluid are evolved by analogous chem- 

 ical changes, in equivalent weights of different ponderable bodies. 

 It may therefore be inferred, that in entering into combination the 

 electric fluid is obedient to those laws of definite proportion which 

 regulate other substances. 



It may be imagined, perhaps, agreeably to the undulatory theory, 

 that the undulations produced at the non-luminous point are such as 

 to destroy each other. But this I conceive would be a surmise re- 

 quiring proof, rather than a fact on which to found an opinion. 



Art. VI. — Of an Improved Barometer Gage Eudiometer ; by 

 Prof. R. Hare, M. D., he. &c. 



About nine years ago* I published an account of a hydro-oxygen 

 eudiometer, in which the measurement of the gases was effected by 

 means of a barometer gage. In the apparatus then employed, the 

 receiver was of glass, and was, of course, fragile. Subsequently I 

 employed a stout iron bottle in lieu of the glass. 



The essential constituents of this apparatus are an air tight vessel, 

 sufficiently strong, and having screw apertures for the insertion of 

 valve cocks, V V V, a thermometer T, and a galvano ignition appa- 

 ratus! W W ; also a barometer gage G, communicating by a leaden 

 tube with the vessel through one of the valve cocks. 



An air pump, pneumatic cistern or trough, and reservoirs for gas, 

 are necessary auxiliaries. 



It is an important characteristic of the barometer gage eudiometer, 

 that it is applicable on a much larger scale than any other. It is 

 only necessary to make the requisite apertures, and tap them for ap- 

 propriate screws, in order to transfer the valve cocks, thermometer 

 and ignition apparatus, with all the essential means of operating, to 

 any air tight cylinder of any size ; to a large cannon for instance, the 

 mouth being closed. The sources of inaccuracy, if any exist, must 

 lessen in proportion to the result, as the quantity acted upon is aug- 

 mented. It would, of course, be safer to extend the cylinder in 

 length than in diameter. 



* The reader of the article then published, will excuse some repetition, as oth- 

 erwise the apparatus in its improved form could not be made intelligible to those 

 who have not seen, or do not remember the explanation then given. 



t This is the name by which I have designated it in my text book. 



