Hi REPORT — 1870. 



are disciisscd, and a semiannmil variation is shown to exist having epochs 

 coincident (or nearly so) with the equinoxes — a conclusion which is shown 

 to be in accordance with similar investigations at Hobarton, 8t. Helena, and 

 the Cape of Good Hope. 



The 8th Section establishes the existence of an " annual variation " or " se- 

 miannual ineqiiality" of the Inclination and of the horizontal and total Forces, 

 derived from the observations made at Kew in 1858 to 1862, with instiii- 

 ments which had been supplied by the Magnetic Office at Woolwich, and 

 employed by Mr. Chambers at Kew. The calculation of the Kew results 

 made at the Woolwich Office was shown to be in accordance with the pheno- 

 mena at Hobarton, St. Helena, and the Cape of Good Hope. 



A subsequent paper, communicated bj" mo to the Royal Society in 1866, 

 contained the Lunar-diurnal Variation of the three magnetic elements derived 

 from the Kew photograms from January 1858 to December 1864, being an 

 extension of two years upon the records discussed in the former paper, and 

 limited only by the epoch to which the photograms had then been carried, 

 i. e. to the close of 1804. The general agreement of the Kew results with 

 those derived at Hobarton and Philadelphia was satisfactorily established by 

 the discussion of the Kew records up to the date of December 1864, and 

 se\eral points of difference in minor respects, requiring further investigation, 

 were indicated : for these the continuation of the Kew photograms, subse- 

 quently to December 1864, may be expected to sujiply the materials. 



(a) 



What appears now to be required is the continuation of the same process 

 of examination, and comparison with the results obtained at other stations, 

 of the results derivable from the Kew photograms in the years which have 

 elapsed since the investigations were completed of which an account had thus 

 been given. 



These additional years are from December 31, 1864, to December 31, 1869, 

 i. e. five years. And this is the work which, if I correctly understood the 

 resolution of the Kew Committee, passed (I think) at the Meeting before the 

 last (viz. in June 1809), the Superintendent was requested to proceed with. 



T rt /^ • J ri EdWAED SaBINE. 



J. F. Gassiof, Li^q., 



Chairman of the Keiu Committee, 



ITo. 2. 



Suggestions by Mr. Stewart as to the best form of Publication of the llesults 

 derived from the Traces of the Kew Magnetographs. 



In the present state of magnetical science, it would appear to be desirable to 

 preserve as completely as possible the details of the original observations, — a 

 course similar to that which has been pursued by Dr. Neumayer in his de- 

 scription of the results of the Elagstaif Observatory, Melbourne. 



Photographic Traces. 



The original documents of the Kew Observatory arc the photographic 

 traces. As these are supposed to be liable to fade in the course of time, I 

 woiild suggest that a careful copy of them on tracing-paper would be the 

 simplest and least expensive mode of retaining them. Such a copy would 

 not be sufficiently accurate for investigations regarding peaks and hoUows, 



