04 KEPORT — 1886. 



through a hole, as mentioned in onr last report, only this hole has not yet 

 been constructed. The thermometers A, B, C, and D have been carefully 

 verified at the Kew Observatory. 



It is proposed to place these thermometers in their respective holes, 

 to expose the instrument to the sun as it will be ultimately exposed, and 

 then to read the thermometers from time to time. If it shall be found that 

 the central thermometer D has a temperature which bears a nearly con- 

 stant relation to the temperatures of the front face as represented by A 

 and B, and of the back face as represented by C, the Committee will 

 proceed finally with the construction of the instrument. If, however, 

 the temperature of D be not related to those of the other thermometers in 

 a sufficiently definite manner, the Committee may require to reconsider 

 the construction of the instrument. 



The Committee have expended 91. 10s. 6d. and returned to the Asso- 

 ciation a balance of 101. 9s. 6d. 



They suggest that they be reappointed, and that the sum of 20?. be 

 again placed at their disposal. 



Second Report of the Committee, consisting of Professor Balfolr 

 Stewart (Secretary), Professor W. Gr. Adams, Mr. W. Lant 

 Carpenter, Mr. C. H. Carpmael, Mr. W. H. M. Christie 

 (Astronomer Royal), Professor Gr. Chrystal, Stafif Commander 

 Creak, Professor Gr. H. Darwin, Mr. William Ellis, Sir J. H. 

 Lefrot, Professor S. J. Perry, Professor Schuster, Sir W. 

 Thomson, and Mr. Gr. M. Whipple, appointed for the purpose of 

 considering the best means of Comparing and Reducing Mag- 

 netic Obsen'otions. Drawn up by Professor Balfour Stewart. 



[Plates I., II., and III] 



It is with deep regret that the Committee record the death of one of 

 their number — Captain Sir Frederick Evans, so well known for the valu- 

 able contributions which he has made to terrestrial magnetism. His 

 eminent scientific qualities combined to make him a greatly esteemed 

 member of this Committee, who now deplore his loss. 



The Committee have added to their number the following gentle- 

 men : The Astronomer Royal, Mr. William Ellis, Professor W. G. Adams, 

 and Mr. W. Lant Carpenter. They could hardly consider their list com- 

 plete without the addition of the first two names, and they are glad that, 

 although not members of the British Association, these gentlemen were 

 not unwilling to serve on one of its committees. 



Since the last meeting of the Association Mr. G. M. Whipple has made 

 a comparison between the method of obtaining the solar-diurnal variation 

 of declination adopted by Sir E. Sabine, and that of Mr. Wild. These 

 methods were applied to three years' observations at the Kew Observatory, 

 and the results were compared with those deduced by the Astronomer 

 Royal from the same three years at Greenwich. The comparison will be 

 found in Appendix IV. to this report. 



The Committee think that this comparison deserves careful study, 

 but they do not feel themselves able to pronounce as yet upon the com- 



