482 Address of the General Secretaries 



totally different kind, modifying the old pressures, and there- 

 fore modifying the old motions, will be introduced. This 

 remark applies even when the phases correspond, if the in- 

 tensities are different. 



Now it appears to me, as far as I can follow the investiga- 

 tion, that some such process has been used as adopting the 

 solution above alluded to, and supposing it to hold with waves 

 of different intensities in different parts of the surface of the 

 small sphere. For the expressions in lines 25 and 28 contain 

 the factor cos 8, which, as it is not differentiated in- the 



du 



operation for forming -r- t but remains still as a factor, seems 



to imply that the wave in each infinitesimal sector goes on 

 just as if there were no other sector near it communicating 

 lateral pressures. 



If I am correct in the view which I have taken of the con- 

 nexion of these steps of the process, I conceive that the in- 

 vestigation must be considered faulty. Of the truth of my 

 first remarks I have no doubt ; but I am less confident as 

 to the exact connexion of the different steps in Professor 

 Challis's investigation; and upon this point I am anxious to 

 be informed. I am, Gentlemen, 



Your very obedient servant, 

 Royal Observatory, Greenwich, December 9, 1840. G. B. AlRY. 



LXXIII. Address of the General Secretaries of the British 

 Association, RODERICK IMPEY MURCHISON, F.R.S., F.G.S., 

 and Major EDWARD SABINE. V.P.R.S, : read at the Meet- 

 ing at Glasgow, September 1840. 



[Continued from p. 449, and concluded.] 



Tj^ROM Zoological researches let us now turn to Physical 

 Geology. One of the most interesting fruits of modern 

 experimental research is the knowledge of the fact, that elec- 

 trical currents are in continual circulation below the surface of 

 the earth. Whether these currents, so powerful in developing 

 magnetical and chemical phaenomena, are confined to mineral 

 veins and particular arrangements of metal and rock, or ge- 

 nerally capable of detection by refined apparatus well applied, 

 appeared a question of sufficient importance to deserve at least 

 a trial on the part of the Association. Our present volume 

 records the result of such a trial on the ancient and very re- 

 gularly stratified rocks of Cumberland, consisting of limestone, 

 sandstone, shale, and coal, so superimposed in many repeti- 

 tions as to resemble not a little the common arrangement of a 

 voltaic pile. Varied experiments, with a galvanometer of con- 



