Wess.—On Local Variations of Atmospheric Pressure. 107 
There being no attendance at the appointed hour, nor for long after it, the 
indefatigable honorary secretary of the club, not caring for a lonely walk, 
abandoned the excursion. Mr. Blair and the writer arriving late, and each 
supposing the usual party to be ahead, undertook the ascent, and they 
presently joined one another. Mr. Blair, who has a keen eye for possible 
railway tracks wherever he goes, was, when I overtook him, engaged in noting 
the height of the barometer, with the view of estimating the elevation of the 
point he had reached, Similar observations were continued throughout our 
walk, which extended to a mile or so beyond the summit, and were repeated 
during the descent at most of the points adopted during the upward 
journey. 
Coming down we noticed an increasing discrepancy between the two sets 
of observations, the new ones showing decreased atmospheric pressure. We 
were, of course, prepared to find that the barometer at the sea level had fallen 
during the afternoon, and expected that the reduction of our observations 
would give us much trouble in consequence, and probably be far from reliable 
as measurements of height. As we began to emerge from the narrower part 
of the gorge through which the Water of Leith flows, we found the difference 
between the first and second observations began to decrease, and finally, when 
we reached the sawmills, the two coincided, which was again the case at the 
intersection of Castle-street and Albany-street, where Mr. Blair made his first 
observation of the barometer. This curious phenomenon caused us some 
perplexity. After consideration I am inclined to attribute it to the effect of a 
fairly strong wind which was blowing from the S.W. when we started, but 
which subsided during the afternoon. In a valley so completely shut in as 
that of the Leith during its upper course, and descending so rapidly from the 
saddle, which lies at about 1,100 feet above the level of the sea, it is certain 
that a strong breeze blowing almost directly into it at the lower end must 
cause increased pressure in the lower strata of air. 
The following is a list of our observations :— 
TABLE OF OBSERVATIONS OF ATMOSPHERIC PRESSURE, 2ND DECEMBER, 1871. 
Points of Observation. During Ascent. During Descent. Difference. 
Castle Street... P S 29°69 29°69 ee 
Leith Bridge... oe eS 29°60 29°60 a 
Ross’ Creek w se 29- 29°53 -05 
rner, Section 7 ... 29°42 29°36 -06 
Nichol’s Stre 29° 29 O07 
Creek 29-20 29:12 -08 
Ford of Leith . 29:19 29-11 08 
thbertson’s . see pie 28°83 28°78 05 
Section peg 5 es es By 28°78 28°74 “04 
Saddle ... fer its vee 2843 tes 
