726 Col. roy’s Experiments for 
extremities; whereas in thehotteft time of the day, that 
difference was generally the greatefl. 
Having been enabled, by means of the cold obferva- 
tions, to form fome judgement whereabout the zero of 
the fcale would fall, below which the equation was nega- 
tive, and above it affirmative; it followed of courfe, that 
the next principal thing to be fought for, was the maxi- 
mum of equation, or that correl'ponding to the higheft 
temperatures the climate of our ifland would afford. It 
was partly with the view of obtaining thel'e that I went, 
injuly 1775, to Snowdon in North Wales. On this expe- 
dition Captain calderwood was fo obliging as to accom- 
pany me, and lend me his affiffance in the operations for 
determining the geometrical height of that remarkable 
mountain. At that particular period, the weather proved 
unfavourable for obtaining hot barometrical obferva- 
tions ; but, in other refpedts, they were very fatisfadtory, 
as being in general conliftent among themfelves, and 
agreeing fufficiently near with thofe of the preceding 
year in Scotland ; at the fame time that they were made 
on a height, as formerly mentioned, greater than any 
■other hitherto meafured, with equal care, in Britain. 
During the fummer of 1776, Dr. lind obtained fome 
more hot obfervations on Arthur’s Seat ; and in the begin- 
ning of the following winter, Captain calderwood 
5 made 
