TRANSACTIONS OF THE SECTIONS. 
67 
These pictures have been since copied and enlarged in the camera by transmitted 
li|ht; and, for this purpose, those developed with the iron have been preferred. The 
excellence of the pictures for transmitted light, whether in copying or illuminating by 
^ lantern, seems to be governed by their tone of colour rather than their upparcut 
cecity. Mr. M'Innes has been very successful in copying and enlarging these pictures 
hr (lie lantern. 
fJn Photographs upon Albumen. By M. Ferrikre. Communicated by the 
Abbe Moigno. 
hiring the reading of this paper a number of very large and beautiful photo- 
Siwed raW1U ^ 3 were ex h*bited, as illustrative of the excellence of the process 
° nMe Chemical Examination of some AUou * of Copper and Zinc. 
By David Forbes, F.G.S.,' A.'l.C.E. 
these were submit♦liTt • . nie P . Vcll ‘ ,w » of a crystalline texture, 
"•'""ds of examination C . he *™ ca t'Xunm*atmn, and the results, ns well ns the 
* reduced to powSJwm h ° ,l110 ^' wl,ich wa * 80 bri,tlc « 8 to 
^Which wwiadoselv - 0U " d C ? nMBl of C0 PP pr l^l.und zinc 53-19 per 
; ' *Mch, on the comrl PIn ' OX,matC t0 tbc du ' ,ni, -'‘‘ ‘^mula Cu. Zn,.. ’1 he yel- 
fl'per and 43.09 Su .?* 8 ,l0t !U n11 brit,lt ' was f °n»d contain 50*91 per 
werc evKlv°dy-r‘ ,nfi WUb M t° rmnU < Zo V ■» ,bat 
v, alloys reproduced 4l l mJ j c « r npomnls. Specimens were ttien shown 
* jj *«• fan. to the fact * A S?'V Uf n,etfl,i • “d P nrt >cular 
' '*®t. lind iw.* ... . act, that a white alloy riinlninino 11 u tr. 
' “clkt'e rosearchei nl 1 .il ® ° } ' s wt ' re ,nvftrinbI y described us yellow; and 
, M ( J?' 8 Porcent, and nnwnv i 0 ^" n ' cmiu , lie(J b >' b "" containing from ns little 
' *, l ' p peculiarity of t{? ? a,Wt T e fou,u ’ ,JC "f a decided, or even dark a allow 
V-:..I a , d “PPear to make i riniai, * silv «*y appearance of the white 
’ bul 110 experimentshull y app 1 j ,lbe t0 tbe manufacture of reflectors or 
cuts nail been made on this point. 
Tb. ^onvS^TL Corn P™ iHon of some Minerals ft 
^ commenced \ 7 *** m ' F G S ' AJ ' CE ' 
r rom the 
m fenced Z , J ' ORH,cs> KGJS - AJ - aR 
^>Su! D f niti °and eyenitic'rocks'of lb ** P 0 ** ° f ° ccum ' nce <* various 
; ''^cou, E ai-a,,c « of hydrous Il l “"'h'Wost const of Norway, and on 
Jjjjcted 1 He then n«s..31S .. m rock9 wh,ch «* generally regarded 
tSSr,"" ~sasz 
H^ tbc «nSi' fe , ls P ar » oud u,icn .I . ,be m.norulogical constituents of 
it was Si SK * bear to tbc development of the 
of th es ; g', st 111 nearly all caiesadi^! d ,‘^ rcc > Wllb toa ‘c particular 
, lb8tuncC8 appeared at the point decomposed 
C mad* Ct “ nd su ™«"dinV the 
Ben ‘ Of the •*£ n °PW, ■ - 
•«JwssH3S«iS 
5* 
