TRANSACTIONS OF THE SECTIONS. 
13 
u when gazing, the image or picture was seen, or, as the author expressed it, 
■ photographed on the retina.” He described the variety of results from different 
drgrm uf transmitted light, and times of gazing, and modes of regulating the light 
prod rating the eyeball, both as related to the colours elicited and the number and 
injure of the photochromatic changes. Pictures of a window were retained for 
•0 hour, whilst breakfast was taken and other objects pursued. By means of 
iurbal black screens, pictures were composed nut of different portions of an illumi- 
'-s‘ed object, and curious dislocated representations of a statuette, &c.» or multiple 
f.urr.i were obtained; and of the sun more than a hundred pictures, with differences 
/colour, were seen at once with the closed eyes. The applications of the experi- 
1 eats lo the examination of the interior of the eye, in ensea of amaurosis, &c., were 
"r< important. The entire series of phenomena would be more than our space 
•uuld permit us to describe in detail, as given by the author; but experience shows 
•1st thi'T vary in their general character in different individuals; and even the same 
itoiviuil finds them different, especially as to the succeeding series of photochro- 
«nhc changes, at different periods of life. 
On a Graphic Method of Correcting the Deviations of a Ship's Compass. 
By Archibald Smith, M.A., F.R.S.E. 
Account of Experimental Researches in Thermo-Electricity. 
By Professor W. Thomson, M.A. F.R.S. 
The experiments described in this paper have been made for the purpose of con- 
mas: thv investigation of various branches of the subject commenced in researches, 
liich an account was published in the * Proceedings of the Royal Society ’ for 
J n °neclass of experiments, thermo-electric inversions, of the kind first 
fr xnv W " £ * >ro ^' f' u,n,n ‘ n K> were sought for between various pairs of metals ; and 
'■‘.H.ITTm va . ri ? tiona of order in the thermo-electric series were found. The 
^ "K table exhibits the results of observations to determine the neutral points 
‘ urnn'i! ?i Me81n whic ^ thermo-electric inversions had been ascertained. The first 
, -ci r . r . n , he tem P e *&ture, Centigrade, at which the two metals opposite are thermo- 
fr,„„ ' oeutra 1 to one another, and the latter metal is that which pastes the other 
' »towards antimony as the temperature rises :— 
P Copper. 
P ,—Brass. 
P j— Lead. 
P j— Tin. 
Iron—Cadmium. 
Iron—Silver. 
Iron—Copper. 
*~l2'2^ Cnt —® rass - (51 Cent. • 
— 1-5 ” ** 1 — Cadmium. 9!) „ 
8-2 " 1 Silver. 121 „ . 
3G " p i—Zinc. 130 
38 .. P a—head. 102-5 „ . 
U . P 3 —Brass. 237 „ . 
U ” \ 2 —'Tin. 280 „ . 
p p " ■••• Lead—Brass. 
i| 8cr very m!,rl! !n n ,e ^ Uee different specimens of platinum wire, which have been found 
It als y an< ^ COnstanl, y ' n dieir thermo-electric qualities. 
!' “dver, at L!!'!** * )rass becomes neutral to copper, and copper becomes neutral 
and ! f h,6h ^mpernture, estimated at from 800° to 1400 ° Cent., in the 
' oh» m l r m 7o ° U to 1000° in the latter. A diagram, showing the results 
IT' 1 ** *t d.ff ere „r" ns ’ anrl orders of the different metals in the thermo-electric 
i. llT 'rt‘. of dJmperaturc*. was exhibited to the Section. In other experiments 
. * 15 found thaPi et li‘ at ' ori 0,1 thermo-electric qualities of iron were tested. 
,. fc ! er ‘he itiflue' 0t J 1 8o ^ iron Wire, longitudinally magnetized when actually 
■ ,J "‘ i,r y*a V . nil ® of a , galvanic helix, and steel magnetized permanently in an 
• ,,<luc ^d 1 exhibit v?° V ? [ rom the magnetic influence by which the magnetic state 
,’7 4, hermo.ei P rr« r7 decided thermo-electric effects of the magnetization: m each 
' c " u *d be nrodnn. < j un ! e 1 nt ' n m^tal homogeneous except as regards niagnetiza- 
*° maLetiS greal facility; the current being always from unmag- 
( through the hot junctions. It is intended to continue the 
