of Edinburgh, Session 1884-85. 
199 
Monday , 15 th June 1885. 
ROBERT GRAY, Esq., Vice-President, in the Chair. 
The following Communications were read : — ■ 
1. On Theories of the Formation of Coral Atolls and Barrier 
Reefs. By John Murray, Ph.D. 
2. Observations on Recent Calcareous Formations of the 
Solomon Group, and their bearing on the Theory of 
Formation of Coral Islands. By H. B. Guppy, M.D., 
R .N. Communicated by John Murray, Ph.D. 
3. Observations, Morphological and Physiological, on Pitch ered 
Insectivorous Plants. By J. M. Macfarlane, DSc. 
4. Preliminary Note on Observations with Aitken’s Ther- 
mometer Screens. By H. N. Dickson, Esq. (Plate VIII.) 
The following results of observations made with four of the ther- 
mometer screens, devised by Mr Aitken of Darroch, form the com- 
mencement of an investigation which has been begun at Granton 
Marine Station, and which is to be carried on there and at Ben 
Nevis Observatory during the summer and autumn, with the view 
of finding a more suitable screen for exposing thermometers for 
meteorological purposes, and, if possible, of determining the mean 
correction to be applied to the readings of thermometers exposed in 
the ordinary Stevenson screens. So far, the work has been entirely 
of a preliminary character, but some points have been brought to 
light which are of considerable interest. 
Mr Aitken’s screens were described in a paper read before the 
Society, on 2nd June last year, and published in the Proceedings , 
vol. xii. p. 661. 
The screen used as a standard with which to compare the others 
consists of a rectangular wooden tube, into which the bulbs of two 
thermometers — wet and dry — are inserted from above, and through 
which a current of air is made to circulate by means of a suction fan. 
The air drawn in by the fan does not come into contact with much 
