On the Lau's of Terreilrial Magnetism. 95 



tilcaliy Dr. Clanny, and J. H. H. Holmes ? Dr. Clanny in his 

 paper on the original safe-lamps, the steam safety-lamps, and 

 the gas-light lamp, states boldly that he was acquainted with 

 the circumstance that explosion would not pass through small 

 tubes; and J. H. H. Holmes, In a libellous advertisement pub- 

 lished in the Scotch and Newcastle papers, accused Sir H. Davy 

 of stealing every thing from Dr. Clanny, except the Doctor's 

 principle of security. I am, sir, respectfully yours, 

 Clidsea, Jan. 2'., 1817. ' W. P. KnigHT. 



XXIV. On the Laws of Terrestrial Magnetism in different 

 Latitudes. By M. BfoT; with Notes by T. S. Evans, 

 LL D. of Christ's Hospital. 



[Concluded from p. IG.] 



/\fter having thus explained all that is at present tnown, on 

 the direction of these two magnetic forces in different parts of the 

 farth, it remains for us to consider their alsolvte intensity. 

 This has been much less attended to than the variation and dip; 

 which, no doubt, arises from its being more difficult to m€asure 

 with exactness. In this department, I know of no accurate ob- 

 .servations except those that M. Humboldt has made in his cele- 

 ])rated Voyages and Travels, and those which M. Rossel made 

 in the expedition of Adikiial d'Entrecasteaux*. 



The 



* It lias already been mentioned, tliat tlie first person who noticed the 

 uiinibcf of vibrations vvliicli a needle maizes in a stated tiiuc, was our in- 

 genious countrvnian, Mr. Cforge Graham, who've experiments are related 

 Hi full len;4th'i!i llie Philosophical Transactions fur 1723, No. 389; or, 

 (lie old Abrid;;nienr, vol, vi. part ii.page 280. I'c hos;an to observe, when 

 itje needle vibratc-ri Jo" on each side of zero. The following are the times 

 jii w liich 100 vibrations were performed. 



Time. 



