Magnetic Variation in the Vicinity of the Cape of Good Hope. 335 



ing from my formula (2) ; but still they are so small as to lead 

 to the following conclusion : — that to Sir John Lubbock belongs 

 the merit of having in 1 840 first pi'oposed a formula containing 

 three constants only, which is capable of giving the pressui-es of 

 vapours with a near approximation to accui-acy throughout the 

 whole range of existing experiments. 



W. J. Macquorn Rankine. 

 Glasgow, October 6, 1855. 



XLIV. On the Magnetic Variation in the Vicinity of the Cape of 

 Good Hope. By Colonel Edward Sabine, Treas. ^ V.P.R.S. 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 13 Ashley Place, Oct. 16, 1855. 



IF you should have room for the accompanying communication 

 in your November Number, you will oblige me by its in- 

 sertion. 



I remain, 



Your obedient Servant, 



Edward Sabine. 



In a letter which has been printed and circulated by the Board 

 of Ti-ade, addressed to Mr. Hartnup of the Liverpool Observa- 

 toiy, by Captain Klein of the Dutch Bark ' Magdalena,' who 

 had been supplied at Liverpool, in April 1854, with a set of the 

 marine meteorological instruments which had been made under 

 the superintendence of the Kew Committee of the British Asso- 

 ciation, and verified at the Kew Observatory, it is satisfactory to 

 read the testimony of an obviously experienced navigator in 

 regard to the efiiciency of the Kew marine barometer. Captain 

 Klein remarks, " I never observed with such a nice and beautiful 

 working instrument as the Kew model barometer. With the 

 greatest motion of the vessel it makes no greater jump than half 

 a tenth ; while at the same time it is so very sensitive, that the 

 series will give a correct idea of the atmospheric tides.^' Captain 

 Klein's testimony cannot but be very satisfactory to the gentlemen 

 of the Kew Committee, and yet more so to Messrs. Welch and 

 Adie, by whose ingenuity and pains the prevailing faults in the 

 ordinary construction of the marine barometer have been greatly 

 surmounted, whilst the price of the instrument has been reduced 

 to about two-thirds of its usual previous amount. 



The object of the Board of Trade in printing and circulating 

 Captain Klein's letter, was doubtless a desire to make his expe- 

 rience of the good performance of these barometers known 

 amongst the owners and masters of our merchant ships, with 



