TRANSACTIONS OF THE SECTIONS. 
7 
polarizer be parallel to the plane of polarization, the relation between the intensities 
uf the two bundles transmitted is 
a sin 3 x=b cos 5 a, whence 
b . j 
—=tg 5 «; 
a 
but we have already consequently 
&=sin s ec, a=cos 3 x, a—b cos 2 x. 
It is not absolutely necessary that the zero of the circle should correspond exactly 
with the azimuth of extinction of one of the two images; two observations may ne 
inade, one on each side of this point, noting the angles, eft, <j>, which corresuo r 
die equality of the images; we then get ac= ^^ — * 
The method just described is evidently applicable to the study of the 
of light reflected from the surface of solids and liquids ; the arrangemen o p 
nor. In ..I nt nln in rillwliil* OTIV flpfillls nGCCSSlltV' 
On the Origin of the Submarine Telegraph and its Extension to India and 
America, liy John W. Brett, London. 
After claiming for himself and his brother, Mr. Jacob Brett, the honour of be’ g 
0I,| y the first inventors, but also the first projectors, of a Sub manne or Oceanic 
' ‘S'aph, the author proceeded to give an account ot the difficulties| I _ , 
,7 ““countered in establishing the first submarine telegraph, " cd that 
working for three years between France and England; and MM 1 
, lftl1 established the submarine telegraph between England and Belg |J* ec i 
which had been in operation since the 1st of May 1653 He then ^ 1 ^ 
“I' difficulties he had encountered in laying down the wo * U S bv OO 
Med Jernmean in July last,-especially in passing a depth 
m 0 J ' v . mt lm<l previously been ascertained to exist on thei ro and 
FneLa ?° r8ica - 11 * depths encountered between LjKSs the 
.,i' d 1111(1 Belgium, did not exceed at their maximum 30 fathom . J 
. tUS?* “h'e wus laid down in the Mediterranean at a depth of 
prcSKrt’IJ c ' ght timcs tlirit ° r thl ' EngUsh Channel. J^fwSSld encounter 
‘ r ‘ passin^.f tbc 8uhma tine cable would part by the great strain QU(1 more 
f artieuln^ l CSe grcal depths ; for which reasons he was strongly .* p iovern . 
y l, y of the most able, and experienced officers ot ^^'^feigbt 
fc ‘l« b?£? C f m B““ d an<1 uldctl lh * undertaking, to make u dc rc kn0Wn not 
t- exceed mdtu d3 0f ? orgo,ia tt,ld Capvija, where the *°’j‘”?" B *. lietll e r he would 
m i.H-ur 5 hUt the great ,K " nt ' tn bC con8ldc . re . d “ # The prudence of 
the*. at ' ri8 * c a total loss of the cable by not doing so. flUeB ti 0 nhe 
.kE*”? Mr - n rett said ho fully admitted; but that it ; *** *£ t0 Cor- 
***, b ut ” e, l to solve at once; for as this telegraph was not * . 8 JJjU greater 
d n'ths niu,t lDe to I,,dia ‘ to be shortly completed to Africa, ^ ^ exp i a i ne d 
the ^cult e e C° Untercd ' 11 WaS ,lccossary t0 te f line had been paid 
°ut, as In. i,.r c * e ncountered in paying it out, when, aftei tl a t a depth 
’Irvine from 'lHff’ a * 0D 6 fbe top of a submarine mountain for so ^ e( ]g e of a 
Pffcipice mf 80 l ° 200 lat -boms, it suddenlv, as he believes, ca , n y depth 
thc 1 arious charts on this route), where it ran out with b 
’•bibitp'd t as ,nade in the workshops of M. Pubo<cq, and bw holier 
“Utuh Association for the Advancement of Science. 
