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XVII. Comparison of Magnetic Disturbances recorded by the Self-registering Magneto- 
meters at the Boyal Observatory , Greenwich , with Magnetic Disturbances deduced 
from the corresponding Terrestrial Galvanic Currents recorded by the Self-registering 
Galvanometers of the Boyal Observatory. By George Biddell Airy, Astronomer 
Boyal. 
Received December 20, 1867, — Read February 6, 1868. 
It would be difficult, even at this early stage in the history of the treatment of Spon- 
taneous Terrestrial Galvanic Currents, to say how the science began * As far as relates 
to my own acquaintance with it, it originated in some general knowledge of the existence, 
on special days, of currents disturbing practical telegraphic operations, which were soon 
found to synchronize with magnetic storms, and in communications with Mr. Edwin 
Clark and Mr. Latimer Clark, both of whom volunteered their assistance, but more 
particularly in conversations, and subsequently in correspondence, with Charles V. 
Walker, Esq. On several occasions, tabular numerical statements were transmitted 
by Mr. Walker to me, and copies of the Greenwich magnetic photograms were trans- 
mitted by me to Mr. Walker ; Mr. Glaisher also went to Tunbridge several times, to 
discuss the subject with Mr. Walker. It is not necessary here further to allude to the 
important papers in the Philosophical Transactions by Mr. W. H. Barlow (1849) and 
by Mr. Walker (1861 and 1862), or to the subsequent observations of Dr. Lamont, 
except for the purpose of remarking that these philosophers possessed no means of 
maintaining a constant record by self-registering apparatus. 
The history of the establishment of apparatus at the Royal Observatory is as follows. 
In my Annual Report to the Board of Visitors of the Royal Observatory, 1860, 
June 2, I submitted to the consideration of the Board, “ It may be worth considering 
whether it would ever be desirable to establish in two directions at right angles to each 
other (for instance, along the Brighton Railway and along the North Kent Railway) 
wires which would photographically register in the Royal Observatory the currents that 
pass in these directions, exhibiting their indications by photographic curves in close 
juxtaposition with the registers of the magnetic elements.” 
The subject having been thus formally opened, and various communications having- 
passed with Mr. Walker as Superintendent and Engineer of the Telegraphs of the South- 
Eastern Railway (in which capacity Mr. Walker has rendered very important services 
to the Royal Observatory), I again, on 1861, June 1, brought the matter before the 
Board of Visitors, in these words : “ I alluded in my last Report to the possible esta- 
* Allusion will be made hereafter to the paper by the late Professor Baelow in the Philosophical Transac- 
tions, 1831, of which, however, the subject is different from that treated here. 
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