TRANSACTIONS OF THE SECTIONS. 
33 
Os Ae Conversion of Relief in a drawing, by inverting the Draiving and 
finnsj ii with a Um of a short focus. By Sir David Brewster, K.H., 
U1.,F.R.S. Land. ^ V.P.'R.S. Edin. 
The eiperiments referred to in this notice were made with photographic portraits, 
Biu« supplementary to those described in the author’s paper ‘On the Conversion 
rfRelief by Inverted*Vision,’ published in the Edinburgh Transactions fur 1844, 
ttlT.p.fiSf. ____ 
0* At Diffraction Bands produced by the edges of Thin Plates, whether 
SoSd or Fluid. By Sir David Bkbwsteu, K.U., D.CE., F.H.S. Lond. 
iKffgiring an accoant of some new results at which he had arrived in the pro- 
*fWiott of thb subject, and showing bow tlie position and magnitude of the bands 
te determined when the iudices of refraction of the hvo media were known, 
kw by this means the indices of refraction of the ordinary and extraordinary 
»>io doubly refracting crystals could he measured at different inclinations to the axis 
•oaofdouble refraction, the author stated that he would not have again called the 
x^tionaftbe Section lo the cuntraversial part of the subject, had not Dr. Whewell, 
*» Isle Work, persisted in asserting that Mr. Airy had completely explained this 
‘j»of phseaomena by the iindulalory theory. I'he author gave a brief notice of 
papers in which Mr. Airy had made this attempt, and showed by a com- 
pjstto of the theoretical with the experimental results, that the undulatory theory 
WsBiifviyfaijgj jjj giving an explanation of these hands. The author also stated 
an-ived at the true explanation of them without any tlieoretical assump- 
Land. ^ V.P.R.H. Edin. 
*«ij)avid Brewster exhibited u map of the dark lines which he had discovered ii- 
itaniH of the solar spectrum, which he hud rendered visible beyond the ex- 
spectrum as given by Fraunhofer; and he explained the construction 
ip»h.iit the nature of the methods bv which he bad observed and pro- 
linos. 
jj. by which these observations were made was executed by Mr. DoHond 
Society of London. The object-glass consisted of two 
i^^tbesame glass, according to the formula of Sir John llerschcl for correcting 
ifWnn ^^'^tion. The cyc-glasses were similarlv con&tructcd. The aberration 
“**w*as not corrected because the light of the object was perfectly homogeneous. 
FtmcHo7is of the Membranes of the Eye at the Foramm 
,S’om»ier»«o. Bo Sir David Brewster, K.H., D.C.L., 
^b.Lond.Sj V.PJi.S.Eim 
which the author deduced from hia observations was, th^t the 
h ia»,^ Well as the retina, was ueccssary in the process of vision. _ 
2? ■ conclusion the author assumed it as a fact that anatomists were 
''ungthat thc/orumra ce«fro/e was a ret 
^M^ical Observatii 
real opening in the retina. 
Observations, by J. U. Crowr, Esr/., Her B>ilannic Majesty's 
of Ror,cay,<U Chrhta^^^^ in the year 1846. ^ 
* continuation of others which havebeen made by this dib- 
V prexeuted to the British Association at the recent 
ofobservatious of the 
'• r-. “ '‘"X- of'-“•.■At”;;,.? 
p.v hk oi me year,at tnenour» ut < -— - - - 
Abn? M ffthe/A^vaowf-frrraadcon the same day and at the same 
^ die m 0/ die barometer' and of the thermometer om the 
10th of each month, and from the 1 Ith to the 20 th, and from the 20 th to 
