266 BAROMETERS WEATHER. 



one-tenth of an inch for every hundred feet elevation, then the 

 Newton barometer, by standing three-tenths lower than that 

 of Selborne, proves that Newton house must be three hundred 

 feet higher than that in which I am writing, instead of two 

 hundred. 



It may not be impertinent to add, that the barometers at 

 Selborne stand three-tenths of an inch lower than the baro- 

 meters at South Lambeth ; whence we may conclude, that the 

 former place is about three hundred feet higher than the latter ; 

 and with good reason, because the streams that rise with us 

 run into the Thames at Weybridge, and so to London. Of 

 course, therefore, there must be lower ground all the way from 

 Selborne to South Lambeth ; the distance between which, all 

 the windings and indentings of the streams considered, cannot 

 be less than an hundred miles. * 



LETTER CV. 



TO THE HON. DAINES HARRINGTON. 



SINCE the weather of a district is undoubtedly part of its 

 natural history, I shall make no farther apology for the four 

 following letters, which will contain many particulars concern- 

 ing some of the great frosts, and a few respecting some very 

 hot summers, that have distinguished themselves from the rest 

 during the course of my observations. 



As the frost in January, 1768, was, for the small time it 

 lasted, the most severe that we had then known for many years, 

 and was remarkably injurious to evergreens, some account of 

 its rigour, and reason of its ravages, may be useful, and not 

 unacceptable to persons that delight in planting and orna- 

 menting ; and may particularly become a work that professes 

 never to lose sight of utility. 



For the last two or three days of the former year, there 

 were considerable falls of snow, which lay deep and uniform 

 on the ground without any drifting, wrapping up the more 



* The best instrument now in use for determining the pressure of the 

 atmosphere, the altitude of any place above another, or above the level of 

 the sea, is the barometer invented and made by Mr Adie, 58, Princes 

 Street, Edinburgh, and named by him tlie sympiesometer. The great 

 simplicity of this instrument is a high recommendation, as it gives the 

 altitudes by a single process of subtraction and multiplication, whereas 

 to obtain the altitude with the common barometer, the use of the barome- 

 trical tables is indispensable. ED. 



