TRANSACTION'S OP THE SECTIONS. 
21 
wpetic pole*- He gave also a short list of substances from both classes, and he 
npressed his view of the antithetical relation of the two lorms of nmgnetic force, 
ud the universality of magnetism either in the one torm or the other. But as 
tief and other points are already published in his papers forming the first part of 
Iklliiioffiphical Transartions for the year 1846, it will be unnecessary further to 
nfcr to them here. 
Exvlence of alta^ating diurnal Currents of Electricity at the ierres- 
ml surface, and tfteir connexioH with the diurnal variatinnof the Magnetic 
Mlt. By \V»LLiA.M Hesry Baulow, MJ.C.E. 
Mf.W.H. Barlow is the engineer of the Midland railway, which was one of the 
aniestlines on which the electric tel^raph was employed. . .-r 
Iheportionof the line on which Uie telegraph is iu operation consists of four mam 
rtsches, all centring in Derby. 
Itl. From Derby almost dirccUy north to Leeds, seventy-three miles, 
hit From Derby to Lincoln, N. 03® East, forty-eight miles. 
3fl From Derby to Birmingham, S. 28*^ West, forty-one miles. 
Itli, From Derbv to Rugbv, S. 16° East, fifty miles. . • • i 
several iinea are all supplied with electric telegraphs, on the principle 
fUtttd by Cooke and Wheatstone, which, although very generally known, »t may 
well concisely to explain. The instrumeuta for immediate observatJon anu tor 
*eTeving signals consist of a coil of fine wire of great length, conlained in a ct^e 
Wbling that of a clock. On a horizontal axis are fixed two C(]ual ma^eUc 
placed parallel to each other, but in a reversed order, so as to be per tc > 
initrsiUtd in respret of terrestrial magnetism, but very susceptible of motion, Irom 
*d«tric corrent passing along the wire through the coil to the earth, or the con- 
from the earth through the wire to the battery. A slight prepouderanw ot 
♦t'jl'tintlic lower branches of the needles renders their natural position vertical; 
ui tie signals are made by causing the ueedle to be dcllccted to the righ or e , 
^rdingly ag the coil-wire is connected with the copper or zinc po e of the batter}’; 
other end of the wire being in counexion with the earth at the distant terminus. 
•*« four instruments at Derby have each on earth-connexion at Derby and at tncir 
termini: at the four placcB aljove-nuincd, ami of course when these m- 
“wieste are not in operation for signals, they are all in connexion with the cartn 
hsA} nod at the four extremities. , •, 
‘ivmsequenceof certain epontancous motions observed in the needles wiion tne 
•‘bniients had only an earth-coonexion, particularly iu times of thunder. 
5^, s fogisler was ordered by Mr. Barlow to be kept of all such apontancoas de- 
5««,amlwas continued for six weeks; and from a careful conipmison ot ine 
JXiKu tics recorded, there appeared strong reason to suspect that, besidi. tne 
^motions, such as those proceeding from atmospheric elecUicity, 
motions which occurred daily in tlie same direction at certain ^ 
J' ^ in a reverse direction at certain other hours, the morning change occurring 
‘'‘‘“1 10 A.M., and the evening change towards the same hour p.m. 
kowever these instruments were freriuontly employed for the serv ^ 
tic case could not be entirely established from Htese i^servations, 
Wm*” belonging (by agreement) to emnlov 
. W^toD duty. Mr. Barlow obtained permission Hiat Company 1 
k.8 proposed further invcsUgalion. He also procun-d very g ^^ded 
•^‘.WMtructed on the same principle im the teJegraph-mstrunJ^b^tsu p 
b,t,ad of circolSr beiing.. and with a facn 
“‘fiteKiastrutnpnrB /.«n«..,i rtKa..«,«h;r.nR tij be made *pgj-'ljy to 
iliiil. • '““‘VBu 01 circular Hearings, aim «• ^ 
m j "wlrtunenta he caused observations to be made luia 
and night, for a fortnight, on the two telcgrapb-h 
both in a tabular “"d onheta- 
to the Royal Society, and from these it appears that 
genemlly vertical ataboutlOA.x... The upper cad 0^0 needle^ tn^ 
iijji. ^^‘^®fiection towards the right-hand, increasing m am 
“w Of the day; they then gradually returned, becoming vertical aga 
_to about the 
again late in the 
