98 
ME. C. V. WALICEE ON MAGNETIC STOEMS AND EAETH-CIJEEENTS. 
We have repeatedly doubled the size of the conducting wire in a given group, and in 
all instances have by the change increased, and to all appearance doubled the deflection. 
This was to be expected with a derived current under like conditions. It was done by 
Mr. Baklow, and with similar results, in 1847*. 
The frequent occurrence of the words “hard over” and “horizontal” in Table I., 
convey a good general idea of the violence of the storm and of the times when the 
greatest activity prevailed. 1 refrain from discussing this Table, because arrangements 
were subsequently made by which observations of a more definite character were made, 
and which have furnished data of greater value. To the examination of these data we 
now proceed. 
In order to form some general idea of the comparative value of the currents that 
present themselves, I selected a telegraph station (Eamsgate) where there was a good 
observer, and where deflections occur at all times of disturbance, even when the ciUTents 
are too feeble to attract attention elsewhere ; and I placed there in the telegraph chcuit 
of the Ashford — Margate group a graduated galvanometer. Certain preliminary expe- 
riments were made with this galvanometer, in order to have some values of its deflections 
with which to make comparison. The results are given in Table II. I first took six 
cells of a battery of amalgamated zinc and platinized graphite, charged with 1 sulph. ' 
acid +10 water, and obtained the deflections with one or more cells when the galva- 
nometer and battery were alone in the circuit. The mean results are given in the fomih 
column. 
The galvanometer was then permanently connected at Bamsgate in the Margate — 
Ashford chcuit, the telegraph length of which is 51^ miles; and ordinary currents were 
sent through the chcuit from cells of the common telegraph battery, the number of cells 
in use being varied. The results are given in the Table ; three cells gave a deflection 
of 5^^, and forty-eight a deflection of 62°; intermediate numbers intermediate amounts. 
It w^as further noted that good telegraph signals produced a deflection of 60° ; middhng, 
one of 64° ; and weak, one of 40°. Having thus a tolerable standard for reference, we 
could observe to better purpose. 
Favourable opportunities occurred very soon after these arrangements were made, and 
of w+ich we were able to avail ourselves, namely, on August 8, 9, 10, 11, and 12, and 
on September 7, 1860. The results are contained in Tables III. to VIII. inclusive. 
These Tables do not contain the whole of the observations made on the respective days ; 
there were other detached or interrupted observations before the commencement or 
after the completion of those tabulated. I have selected a portion of each day during 
w+ich there was the least possible break of continuity in observing. For instance, on 
August 8, out of 6^ 44™, only 37™ are blank ; on August 12, only 21™ out of 10*^ 31™, 
and so on (see Table IX. h). The “ time” column is accurate. All the observing stations 
receive time signals direct from the Royal Observatory, Greenwich, at least once a day. 
The “ duration ” column is subdivided into two parts, marked N. and S., which contain 
the time in minutes during which a positive current was flowing from the N. to the S. 
* Philosophical Transactions for 1849, p. 63. 
