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 same 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- 



