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British Association for the Advancement of Science, 295 
tain, making certain simple allowances for temperature, the height 
at which the barometer would have stood at the-station on the 
hill can be deduced ; and. thence, by the usual calculation, the 
height of the station. . The stem of the instrument is previously 
graduated, so that bare inspection shows the es of es air at 
the elevated station. - 
Sir D. Brewster communicated the following papers: “Ona 
new phenomenon of Color in certain specimens of Fluor-Spar.”— 
“On an Ocular Parallax in Vision, and on the law of visible di- 
rection.”—‘ An account of certain new na of Diffrac-. 
tion.” ——“ An account of an analogous series of new phenomena 
-of Diffraction when produced by a transparent diffracting body.” 
—‘ On the combined action of grooved metallic and transparent 
surfaces upon Light.” These valuable papers called forth from 
Sir J. Herschel the highest praise. “There is extreme difficulty,” 
said he, “in following with sufficient rapidity for discussion, such 
an. absolute torrent of new matter. Indeed, the discoveries of 
Sir D. Brewster, whether viewed in relation to the intervals at 
which they succeed each other, or. the instruction they ost veys 
equally fill us with delight and astonishment.” 
A paper on the Helnv Wind of Crossfell, was read by Rev. J. 
Watson. 
»Dr. Smith vend J a paper on the Varkitions. in the yaicnndity of 
Rain which falls in different parts of the Earth. The causes 
of these variations are, the author imagines, to be ascribed to the 
physical differences of the vicinity of each place, and in the track 
of the most rainy winds; and he found this opinion confirmed by 
a long average of Westerly and Easterly winds at London, com- 
pared with six other places. — . 
Prof. I esntitons- staal paihe-ai Bitlet Finisjtnioorite 
, an instrument for tllustrating its phenomena. The 
Stereoscope 
instrument is so named, from its property-of presenting to the 
mind the perfect resemblances of solid objects. A short explan- 
ation of the principles of the instrument was offered by Prof. 
W. Sir D. Brewster feared that the members could scarcely 
judge from.the very brief and modest account given by Prof. W. 
of the principle and-of the-instrument devised for illustrating it, 
of its extreme beauty and generality. He considered it one of 
the most valuable optical papers which had been presented to the 
' -He observed,.that when taken in conjunction with the 
