TRANSACTIONS OF THE 6ECTIONS. y 
miles of gutta percha covered copper wire, show that the voltaic or magnetic impulse 
varies in velocity, through such conductors, from 960 to 1700 miles per second, 
according to the intensity of the current employed. _ 
The diminution in velocity, as regards the underground wires, is intimately con- 
eectrd with the recoil current recently analysed by Dr. Faraday, and is due to the 
oiuWv between such conductors and a Leyden jar, the charge cnnmiunica e 
'• log temporarily absorbed by the wire until the moss of copper is saturated with 
electricity. Hence a retardation ensues to a less or greater degree as the intensity 
rf the current is increased or diminished. . . 
From the foregoing I deduce that the upeed with which electricity passes, varies 
with the energy (i.e. intensity) of the current employed, and ulso with the nature or 
renditions of tiie conductor interposed through which it passes. 
I ndergronnd wires are only affected by terrestrial electricity when a now takes 
from one district of the earth’s surface to another ; while overground wires 
ur also subjected to the action of perturbative currents whenever the electrical 
' itnlw * of the atmosphere changes as regards the earth—principally with the rise 
w fall of dew, or during aurora borealis. 
Fhf ‘ Quarterly Review’ for June 185-1 contains a most erroneous comparison 
i*tween the English and American telegraph charges. The American rate for a 
mc ***ge of fourteen words between Louisville and Pittsburgh is stated by the 
lUwicw ’ to be sixpence halfpennv, whereas, upon reference to the United States 
felt-graph Tariff.’ published in April last, the cost of such a message is two 
•lulling* and eightpence, while the English charge for a similar communication an 
'•(ual distance (between London and Liverpool), prior to the publication of the 
K,vuw .’was two shillings and sixpence. Twenty words might be sent in this 
Gantry I’ 1 "' the same amount (two aud sixpence), while in America the charge 
would be three shillings and sixpence. 
v ll ' r ' Quarterly Review’ also states that the cost of a message of ten words from 
» ew lork to New Orleans is two shillings and sevenpence. Upon referring to the 
Ijfrican tariff scale it is found to be ten shillings. 
llu -' greaterceconomy claimed by the 'Review' for America does not exist, but 
» advantage is on the English side ; and 1 therefore hope that this refutation wi 
^ impression so injurious to the system of our country from being generally 
atl A PP<tralus for clliptically-polarized Light. By M. Dove, Berlin. 
pr * ^. of 136 ‘ nc ‘dent in a plane perpendicular to the edge of an 
othrr’, d , ,n , ad,rect ‘ on pa«lle* to the base (or face equally inclined to the two 
it, ril 7’ llle refracted ray, after being totally reflected at the base, emerge at the 
be a ,' !■ tlu? emergent my will be parallel to the incident, and its course may even 
I- I r ,,,! inUatl ,' ,u of thfU of the incident ray. If the incident ray be polamed, the 
•r,' , in Wl11 modified by total reflexion. If now two such prisms, of proper 
l iru i : , L “? oun ted in a tube, so that their edges are perpendicular, and then ase ® 
U.c • ,L 1 " ! of the lnbe - and one of the prisms be moveable about the axis of 
l-n„ ,, ■;;STW n ? tube in the direction of the axis will pass through both 
fUfi-d Kith th 1, ^® v,atlon * whatever be their relative azimuths. It the P' ,s . 
^' : ‘r,-d l tb : ,r , bas ; 8 perpendicular to each other, il is plain that m case the ray be 
roiiud thmitwo of . l ,olur 'Nation Will nut be changed ; but if one prism be turned 
varieties of ’ tbe e ®’ ects °f the two total reflexions will conspire. In X 
'ithijiit fi.p ?^, L> *p tlca l 1 y*polarized light, from plane to circular, may be P r ° d u cad 
eral transport of the ray, which is so inconvenient in 1' resnel s r o 
The aui?” * 0WC ‘^ tercosco P‘ c Phenomena. By M. Dove, Berlin. 
,n Co, »en 1I e 0 ncr aS r C i- iefl - v induced to draw the attention of the Section to this subject 
lotting, having lJuv ‘ d Brewster, who he greatly regretted was not a 
,bc author hnH S ; enied . al tbe Belfast Meeting the soundness of the explanation 
tb * metallic |,uf Ven tlle cetu «« of the appearance of those bodies which ex i 
Ustre ' T his he considered to arise from the superficial layers of par- 
