VOL. XLI.] PHILOSOPHICAL TRANSACTIONS. 487 



that the mean height of the barometer, for the whole 14 years, is 2Q.58 inches; 

 the mean quantity of rain annually, 23 inches; and the mean altitude of the 

 thermometer 56,52,48, that is, at the coldest time of the day 56, at the hottest 

 48, and their mean 52. The thermometer made use of, was that of Mr. 

 Hauksbee, and kept constantly in the same place. And the altitudes of the 

 thermometer are taken but twice a-day, viz. at the coldest, which is at sun- 

 rise, or sometimes a little after; and at the hottest, viz. between 2 and 4 in 

 the afternoon : by which method are gained the proportional heats for every 

 month in the year, and their difference, as also between that of day and night, 

 for 13 years together. 



Mr. Lynn was not a little surprised to find, in casting up the column of the 

 mean altitudes of the thermometer collaterally, that as those for July, being 

 the hottest month, are 4 1 .354-,30, so the altitudes of June and August, on 

 each side of it, come out exactly equal to each other, and also those of May 

 and September; these last only differing in their morning and evening heats or 

 altitudes, which does not alter their medium of 44-i-. The following are some 

 few remarks added on the weather. 



When there is a haziness in the air, so that the sun's light fails by degrees, 

 and his limb is ill defined, it is a pretty certain sign of rain, especially if the 

 mercury falls. The like haziness, at night, is still more a sign of it. It is 

 observable, that though the mercury, in the summer months, does not so much 

 vary in its altitudes, as at other times of the year; yet in that season we have 

 the most rain; it should seem therefore, that the different warmths, and con- 

 sequently rarefaction of vapours, in the upper and lower currents of the air, 

 and those currents mixing, and sometimes wholly interchanging, are then the 

 more immediate causes of the rains, if not also of thunder and lightning. — 

 Black fleecy clouds, formed on a sudden flurry of the wind, are generally suc- 

 ceeded by a shower: and, the shifting of the wind in a little time almost round 

 the compass, in hot weather, is often succeeded by a thunder-shower. — Several 

 times, when the mercury has been a good while high, and so continues, there 

 has fallen misling rain ; especially about the new and full moon, with an easterly 

 breeze, which the borderers on the coast of Lincolnshire and Norfolk call tide- 

 weather, and may be occasioned by the vapours arising from the tides, which 

 then cover a vast wash of sands in their neighbourhood. — Those vapours some- 

 times reach us here in Northamptonshire, but seldom further west. — The nights 

 are for the most part calmer than the days; and the winds seldom settled in their 

 quarter, or at their strength, till some hours after sun-rise, and generally die 

 away again before sun-set. 



