430 Different “ Rates” of Pennington’s Astronomical Clock, 
on our several operations in concert, serves as a natural break- 
water to the fine harbour of Balta Sound, and is separated from 
Unst (towhich M.Biot’s apparatus was removed after he quitted 
us) by two narrow straits. After tents were set up for M. Biot, 
for ourselves and the soldiers who accompanied us, a temporary 
house, with walls of stone and a strong tarpaulin cover, was erected 
for the reception of the astronomical clock and transit instru- 
ment; and suitable spots within a few yards of this were chosen 
for the establishment of the great theodolite tent, and that for 
the zenith sector. Mr. Edmondston’s house at Buness, in Unst, 
where M. Biot ultimately fixed his station, was within sight of 
ours: the distance being about two miles and a half, and bearing 
nearly west by north*, 
The house in which the clock was placed, stood at an eleva- 
tion of 121 feet above the level of low water in Balta Sound, 
and in north latitude 60° 45’ 3”. ‘The transit instrument being 
adjusted to the plane of the meridian, by one of the methods 
described in Ludlam’s Astronomical Observations, published in 
1769, and confirmed by means of the elongations of the pole- 
star observed with the great theodolite by Captain Colby, a suit- 
able meridian mark was fixed, at the distance of more than two 
miles on the islandof Unst. The pendulum of the clock was set 
in motion on the morning of July 30, 1817. On the next day, 
when it seemed to have attained its full rate, its semi-are of vi- 
bration was 2° 20’; and thus it continued until August 17th, 
when the clock was taken down, and its parts returned to their 
respective boxes. 
Were I here to copy the entire record of my observations with 
the transit instrument much room would be uselessly occupied 5 
because the mean or reduced time upon the five wires in no in- 
stance deviated more than three-tenths of a second from the time 
on the meridian wire, and usually agreed to about one-tenth of 
asecond. I shall, therefore, reserve the entire publication of 
these to a more suitable time and place, and here simply pre- 
sent results. They are sufficiently numerous for the purpose ; 
but not so numerous as would have been obtained ’in the same 
interval, in a climate better suited than Zetland for astronomical 
observation fT. 
* Buness is, in fact, as little above the level of the sea, as any point 
which could have been selected in the north of Zetland. It is almost entirely 
surrounded by hills, at no great distance ; and was, therefore, in my opinion 
as well as Captain Colby’s, altogether unfit for an astronomical station, 
from which triangulation was to proceed ; however much the hospitality of 
Mr. E. might render it an agreeable residence. 
+ From J july 22d, to August 17th, we had but one day that was entir ely 
free from rain: though during the whole interval we were but once visited 
with a fog, and that ‘did not last more than an hour. 
Taking 
