302 



The inclination appears to me to be very incorrect in the meridian 

 of Alexandria. In India the few results of Elliot's given in the 

 Phil. Mag. from the Proceedings of the Royal Society, accord ex- 

 tremely well vvith my calculations. I subjoin a few points of com- 

 parison : — 



North Pole in 70° V N., 263° 37' E. Ross's observations give 

 70° 5'' N., 263° 14' E. For the South Pole, 74° 6' S., 152° 47' E. 

 seems to agree less closely with Ross's map, although the inclina- 

 tions observed in the neighbourhood agree well with the calculated 

 ones. „ . 



o / o 



Maximum of total force hi the northern hemisphere 1871'8 in 54 21 N. 265 53 E. 

 (Error compared with Lefroy's observations -f 6*4 in 54 IN. 260 1 E. 



+0-8 in 55 6 N. 267 4 E.; 



+4-6 in 50 2 N. 264 E.) 



For the force in the southern hemisphere, 2027 '6 in 64° 36' S., 

 144° 34' E. is perhaps less correct, but there are in the S. hemisphere 

 some striking aiiomalies in the observations. 



The probable error of the force is 19*1 ; if however some groups 

 which are at any rate not very correct are omitted, it becomes a little 

 less than 15. For the inclination, 31'"1 ; for the declination, 41''3. 



I have gained my principal object in the work by becoming my- 

 self better informed, but I have thought it might perhaps not be 

 wholly useless to others if only to stimulate travellers to make ob- 

 servations for comparison, and I have therefore been at the pains of 

 writing out the table of comparisons (a task more irksome than that 

 of calculation). But to publish is very difficult; on such a subject, 

 and under present political circumstances, no bookseller in Germany 

 would undertake it. The Admiralty at St. Petersburgh would per- 

 haps print it in their Memoirs, but in the Russian language, in which 

 it would be as good as buried ; I turn to you, asking whether it might 

 not be possible to get it published in England, not as a separate 

 work, for perhaps no bookseller would accept it, but in a collection of 

 similar papers. To me it would be most agreeable if it could appear 

 either in the Reports of the British Association or in the Philosophical 

 Transactions ; and by preference in the latter, because I have derived 

 from thence the best part of my materials, besides which the first re- 

 sults have already appeared in the Proceedings of the Ro^'al Society. 

 You will be best able to judge for me ; I do not know v^^hat is the prac- 

 tice of either of those bodies in regard to writings not by their own 

 members. My memoir is, I fear, long, but yet it consists chiefly of the 

 table of comparisons. Of maps, I give declination, inclination and 

 total force, two of each (Mercator and Polar). Unluckily I have 

 no translator here who understands the subject, so I could only 

 make the attempt myself, and as the memoir consists chiefly of figures 

 from whence simple deductions are derived, there cannot be great 

 errors ; in the rest pray make the needful alterations where there 

 are glaring Germanisms, if you think it possible the whole may be 

 printed. If not, pray send me back the MSS. at some future time, 

 not for publication, but for my own use. I finished yesterdaj^ and 

 send this week to the British Embassy ; only I repeat my prayer, 



