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of Edinburgh, Session 1868 - 69 . 
and minimum of temperature may be ascertained between any 
given periods of time ; and this is still the method usually preferred 
for ascertaining the daily maxima and minima. In 1795, Mr 
Alexander Keith, afterwards our benefactor Sir Alexander Keith 
of Ravelstone, describes both a thermometer and barometer, which, 
by the application of the same kind of contrivance to each, may be 
made to register the state of these instruments continually, with 
the aid of clock-work. Mr Macgowan contributes meteorological 
observations for six years, ending with 1776, made at Hawkhill, 
near Lochend, in this neighbourhood ; the Duke of Buccleuch, 
President of the Society, contributes the observations of ten years, 
ending with 1783, made at Branxholme, his seat in Roxburghshire; 
and Playfair adds abstracts of observations, made at Windmill 
Street, in the city, for six years, ending with 1798. In 1796, Dr 
Balfour of the Bengal Medical Service reproduces an inquiry 
made a good many years previously, in which, by regular half- 
hourly observations, he was the first to ascertain that at Calcutta, 
near the equator, the barometer observes a double diurnal revolution 
of about a tenth or twentieth of an inch, the highest positions 
being at ten in the forenoon and evening, and the lowest at six in 
the morning and afternoon; and in 1799 Playfair points out that 
this result had been also obtained in 1785 by independent observa- 
tions made near the equator by Lemanon, a naturalist attached to 
the ill-starred expedition of La Peyrouse. 
Mr Hall of Whitehall describes a remarkable lunar halo, con- 
sisting of a small concentric ring, of about ten degrees in diameter, 
round the moon, and a great ring, seven or eight times that 
diameter, wdiich passed through the moon, cutting the concentric 
halo in two. Playfair describes a rare rainbow which he saw over 
the sea from Dunglass, consisting of a lofty perfect primary arch, 
almost a complete semicircle, and a secondary bow springing from 
the south limb of the other, and bending outwards in a southerly 
direction. The Reverend Dr Graham of Aberfoyle notices an 
Aurora Borealis which he observed at that place in the day-time on 
February 10, 1799, at half-past three, and states his belief that 
this was only the second on record, but conjectures that such 
observations would not be infrequent, if frequently searched for in 
the circumstances he describes — viz., “when the sky, being for 
