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have to be strictly periodic. The experiment would he well worth 
trying, but it would involve great difficulties as well as considerable 
expense ; and it might fail altogether on another account, viz., the 
breadth of the individual sodium lines. 
I find it advantageous to replace the second Nicol by a double- 
image prism, and to take the reading when the two images of the 
slit are equally bright. 
BUSINESS. 
The following candidates were balloted for, and declared duly 
elected Fellows of the Society: — J. M. Thomson, Esq., King’s 
College, London, W.C.; Dr C. G. Knott, Natural Philosophy 
Laboratory, University, Edinburgh; Dr J. A. Russell, Woodville, 
Canaan Lane, Edinburgh ; W. W. J. Nicol, Esq., 15 Blacket Place, 
Edinburgh ; Charles Prentice, Esq., 8 St Bernard’s Crescent, Edin- 
burgh ; L. L. Rowland, M.A., M.D., Williamette University, Salem, 
Oregon, U.S.; Robert Pullar, Esq., St Leonard’s Bank, Perth; The 
Rev. Professor Flint, Johnstone Terrace, Craigmillar Park ; De 
Burgh Birch, M.B., C.M., 19 Albany Street, Edinburgh; J. Berry 
Hay craft, M.B., B.Sc., Physiological Laboratory, Edinburgh. 
Monday, 15 th March 1880. 
The Right Rev. BISHOP COTTERILL, Vice-President, 
in the Chair. 
The following Communications were read : — 
1. The Topography of Jerusalem. By Lieut. Claude 
Reignier Conder, R.E. 
The subject on which I have the honour of addressing you this 
evening is one far more complicated and difficult than that of the 
paper which I read to the Royal Society of Edinburgh some short 
time since. We have to deal, not with the surface of a country and 
the position of places of which the ancient names are still extant, 
but with a ruined city, buried to a depth of from 30 to 50 feet in 
rubbish on which modern buildings having been erected, and with 
