364 Capt. Kater’s experiments for determining the variation 
This correction, together with 0,23 (the correction for the 
height above the sea) being added to the mean number of 
vibrations, we have 86086,10 for the number of vibrations 
which would be made in a mean solar day, in vacuo, and at 
the level of the sea. 
The difference between this result and that of the first series 
of experiments made under the most unfavourable circum- 
stances of acceleration in the rate of the clock, being only 0.09, 
affords it is presumed a most satisfactory proof that no very 
important error is to be dreaded from this source in the obser- 
vations at Unst. 
Operations at Leith Fort. 
Having completed the requisite observations for the latitude 
of my station, and for connecting it with Cowhythe, I quitted 
Portsoy for Edinburgh on the 20th August, leaving the instru- 
ments and party to come by sea. 
Leith Fort was my next station, and here, as I could pro- 
cure no lodgings in the neighbourhood, an officer of the Royal 
Artillery most kindly relinquished to me his quarters in the 
barracks. The Cherokee arrived on the 28th, and the instru- 
ments were landed the same evening. 
On my first arrival at Edinburgh to embark for Unst, I had 
been introduced to Sir Howard Elphinstone, the chief engi- 
neer of the station, and received from him the assurance of 
every assistance in my experiments, which his department 
could furnish. Though to my regret he was now absent on 
duty, I was promptly supplied with such materials and arti- 
ficers as were necessary, and on the 29th August my appa- 
ratus was firmly put up in one of the public store rooms of the 
Fort, which was excellently adapted to the purpose, and the 
v 
