goo The Rev. F. J. H. Wollaston on the 
measure at its utmost limits 1900 feet, it was necessary, 
on a height of 3550 feet, to divide the whole measurement 
into two, or, for greater security, into three lengths, and it 
became therefore a fair trial of the practical use of the in- 
strument in every respect. 
On the 24th of August, having occasion to ride from Car- 
narvon to Gregory’s New Inn, near Llanberis Lake, at the 
foot of Snowdon, for the purpose of securing accommoda- 
tions for my party, I took the instrument in my pocket, 
having previously boiled it on the ground floor of the Vicar- 
age house at Carnarvon, where it stood at 517,5, thermo- 
meter 66°, barometer 30,0. In the parlour at Gregory’s it 
stood at 401, thermometer 66°, barometer not changed during 
my absence ; difference at the two stations 1 16,5. 
100 : 116.5 : : 2 3^ : 2 75 feet, the approximate height: 
add the correction 0,089 
x 275 from Generali 24.5 
Roy’s table following ) 299,5 f eet: > the corrected height 
of Gregory’s above the Vicarage. 
The descent from the Vicarage to the north end of Car- 
narvon quay, was taken by levelling, and found 11,25 feet. 
August 27. The instrument had been set at Gregory’s at 
768, before the party began to ascend the hill ; but when we 
came to the place where the guide supposed we had ascended 
half way, it stood at about 300, showing that we had not 
gone far enough to take the whole in two lengths of the 
scale; and we therefore proceeded farther, to a point oppo- 
site a pass in the ridge of Snowdon, called Bwlch Cymbrw- 
nog, by which the hill is ascended from Nant. In carrying 
the instrument incautiously from the former point while 
