MEMOIR OF DR. WALKER. 27 
Duddingston Loch. But the franking act obliges 
me to stop. 
“ I ever am, 
Your Lordship’s devoted Servant, 
John Walker.” 
During this excursion he ascended the two high 
mountains called the Paps of Jura, chiefly for the 
purpose of making two experiments; the one to 
measure the height of the highest mountain, by the 
barometer, at its base and upon its summit; the 
other to ascertain whether boiling water is not of 
the samo degree of heat at the top of a mountain 
that it is at the bottom, or is visibly colder, by the 
thermometer, upon the mountain than upon the 
plain. 
His account of this excursion is beautifully told. 
“ Upon the 27th of June we filled a barometer at 
the shore of the Sound of Isla, at seven o’clock in 
the morning ; and being placed at the level of the 
sea, the mercury stood at twenty-nine inches and 
seven-tenths. At ten o’clock it stood at the same 
height, when we set off in order to ascend the 
mountain, which is one continued steep from that 
point of the shore. Some Highland gentlemen were 
so good as to go along to conduct us ; and a box 
with barometrical tubes, a telescope, large kettle, 
water, fuel, provisions, and a couple of fowling- 
pieces, loaded seven or eight servants. 
“ The first part of our progress lay through deep 
bogs, from which we sometimes found it very diffi- 
