Proceedings of the British Association. 43 



moment when it is neither increasing nor diminishing in tempe- 

 rature, which will be a little before sunrise. If this is a true ex- 

 planation of the four fluctuations of the barometer in a day. it 

 will follow that the morning rise ought to be greater at consider- 

 able elevations, provided they are not too great, because some of 

 the air will be lifted above the place of observation ; and such 

 was found to be the case by Col. Sykes in India. As this morn- 

 ing rise of the barometer depends on the increasing elasticity of 

 the air, and this increasing elasticity, on heat, Mr. E. proposed to 

 the mathematicians to calculate how much the whole atmosphere 

 is heated from sunrise till the time when the barometer stands 

 highest, the actual rise of the barometer being given. In this 

 way meteorology may assist astronomy. Prof. Forbes doubted 

 the correctness of Mr. E.'s views of the great daily fluctuations 

 of the barometer at elevated stations : for, towards 2 or 3 o'clock 

 the heat being greatest, its effect in lifting up the inferior air to 

 and above the elevated station, should then be greatest, whereas 

 that time of the day was nearer to the time of minimum height 

 of the barometer than of its maximum. After the announcement 

 of the titles of a few other papers, the business of the Section was 

 concluded. 



Sect. B. Chemistry and Mineralogy. 



A paper on some electrical phenomena, and on a supposed neiu 

 substance, was presented by Dr. Schonbein. It is well known 

 to electricians that in certain electro-chemical decompositions a 

 peculiar odor is evolved, very analogous to that produced by com- 

 mon electric sparks, or by the working of an ordinary electrical 

 machine in the air. Dr. S. has undertaken a series of experi- 

 ments in order to ascertain the circumstances under which this 

 electro-chemical odor is evolved, the causes which influence its 

 production, and if possible, the principle to which its appearance 

 is to be attributed. This peculiar odor is evolved at the anode 

 or positive surface, when certain aqueous solutions are decompo- 

 sed by the i)assage of a voltaic current. The oxygen gas which 

 is then evolved has a strong and peculiar smell, which is perfectly 

 similar to that which is always perceived when an electrical ma- 

 chine is worked or sparks passed through the air. M. Schonbein 

 has observed that the odor is evolved on the decomposition of 

 water, dilute sulphuric acid, solutions of phosphoric and nitric 



