Miscellaneous. 79 



in sereral Momoirs, some of which hare been translated into 

 I'.nglish. Again, the researches of Humboldt, Buch, Wahlen- 

 berg, and reost recently Kupffer in a Memoir on Isogeothermal 

 Lints, read before the Academy of St Petersburg, in 1829, have 

 shown that the lempeiature of the earth differs in many parts of 

 the gl be from that of the air, being generally in defect below 

 lat. 56", and in excess beyond it. The progiessive increase of 

 temperature with that of the depth in Artesian wells, and the 

 deviation of the mean temperature of the Earth from that of the 

 Air iu different latitudes, have opened new fields for discussion ; 

 and by the zealous co-operation of observers cannot fail to present 

 results, of which at present we can form but an imperfect idea. 



Magnetism. — It appears to the Committee highly desirable 

 that a series of observations upon the Intensity of Ttrreslrial 

 M.K/netism in various parts of England he made by some com- 

 petent individual, similar to those which have recently been 

 carried on in Scotland by Mr. Dunlop. 



Should the Committee succeed iu finding some individual 

 ready to undertake the task, they propose that an applit-ation 

 should be made to the Royal Society of Edinburgh, for per- 

 mission to make use of the Standard Needle belonging to them, 

 and constructed under the direction of Professor Hansteen of 

 Christiania. 



It appears to the Committee of considerable importance, that 

 a certain number of observations should be made throughout 

 Britain with the Dipping Needle, iu order to reduce the Hori- 

 ;iontal to the true Magnetic-Intensity. 



Note The time of three hundred vibrations should be observed, and 

 the methods of observation and rerl action should be the same as 

 have been emplojed and described by Humboldt, Hansteen, and 

 others. 



Electro- Magnetism. — The Committee recommend, as an im- 

 portant subject for further prosecution, the examination of the 

 Electro Magnetic condition of Metalliferous Veins. The Com- 

 mittee would refer for the details of what has been already 

 done upon this subject, to the Paper of Mr. Fox in the Philo- 

 stiphical Transactions for 1830 ; and would propose that the 

 experiments should he extended to veins which traverse, as in 

 some of our mines, horizontal and dissimilar strata. 



Tides. — M. Daussy has shown, that on the coast of France, 

 between Oiiessant and the coast of Spain, the Atmospheric pres 

 Pure has considerable influence upon the height of the tide one 

 inch of rise in the mercurial column depresses the tide fourteen 

 inches. He found that the influence of the wind upon the height 

 of high-water is insensible. M. Ludbock has ascertained "that 

 in the river Thames tho influence of the fluctuations of the Ba- 

 rometer upon the tide is insensible or very nearly so." [le has 

 also found '•' that the direction of the wind (unJcss in violent 

 gales) has no efi'ect upon the phjenomena of the tides in the river 

 Thames." 



