110 ae REPORT—1862. 
“advantage of verbal explanations by the Rey. Robert Main, who was there 
at the moment, besides the written explanations kindly given to him by 
Mr. Airy.” He thus became well acquainted with the localities, arrange- 
ments, and instruments, of which he gives a detailed description; but as he 
ultimately preferred ordering for his own Observatory instruments on the 
pattern of those employed at Kew, we may pass at once to his account of that 
establishment, which will be given nearly in his own words :— T 
« The Observatory at Kew, besides occupying itself with meteorological 
and magnetical phenomena, and the photographic registry of the spots of the 
sun, verifies meteorological and magnetical instruments, compares them with 
the excellent patterns which it possesses, determines their constants, and 
improves the methods of observation. The Director (Mr. Balfour Stewart) was 
absent ; but Mr. Chambers, assistant observer, and Mr. Beckley, mechanical 
engineer of the Observatory, attended me so obligingly, and with such sincere 
desire to satisfy all my importunate inquiries, that I derived great profit from 
the visit. 
“The self-registering magnetic instruments at Kew were constructed in 
1857, about ten years after the registering apparatus at Greenwich was 
adapted to the previously existing instruments at that Observatory. Based 
on the same general principles, they differ in size, and in certain happy 
innovations introduced by Mr. Welsh and executed by Adie (a skilful artist 
in London). They have been in action since 1858, and give results which 
leave nothing to be desired. 
«« The locality in which the self-registering magnetic instruments are placed 
at Kew is in the basement-story of the building, which was formerly an 
astronomical observatory: the choice was determined by a condition which 
should never be lost sight of, viz. the greatest attainable constancy of tem- 
perature.” 
[Having already described the magnetographs at Greenwich, Prof. de Sotad, 
whilst giving a very elaborate description of the Kew instruments, dwells at 
length principally on the points in which they difier from those at Greenwich ; 
but the deseription is here omitted, as the Kew instruments have been care- 
fully and well described by Mr. Balfour Stewart in the volume of Reports of 
the Aberdeen Meeting of the British Association, p. 200-228. Prof. de Souza 
proceeds as follows :— 
** A short time before my visit to the Observatory Dr. Bergsma had been 
there, sent by the Dutch Government to examine the magnetographs 
destined for an observatory in Java, and constructed on the Kew pattern. 
I may say in passing that this examination consists in receiving practical 
instruction on the mode of manipulating with the instruments, in assisting 
in their collocation in the verification-house, and in the determination of 
constants. Some modifications were introduced in Dr. Bergsma’s magneto- 
graphs which I will now notice, and which constitute their last state of 
improvement. 
«The great bell-glasses which rest on the marble disks were replaced by 
eylinders of gun- -metal surmounted by smaller glass cylinders. Each has an 
aperture to which is adapted a plate of glass with parallel faces, taking the 
place which in the great bell-glasses was occupied by the openings of the 
glass plate and of the achromatic lens; by this new arrangement the aechro- 
matic lens is independent of the cylinder, and can be brought near to, or 
removed further from, the mirror according to convenience. In this manner 
any disarrangement of the cylindrical glasses, or the taking of them away, 
does not alter the position of the lens, or interrupt the march of the magneto+ 
