at the Island of Balta, and at Woolwich Common. 433 
We may now proceed to detail more briefly the observations 
to determine the rate of the clock at Woolwich Common; 
omitting as unnecessary the register of the barometer and ther- 
mometer: of which the former oscillated between 30-402 and 
29-464, the latter between 54° and 42°, 
The hall of my dwelling-house having a window that opened 
to the north, from which | could conveniently observe several cir- 
cumpolar stars, the clock was set up there November 15, 1817; 
the proposed observatory at the Royal Military Academy not be- 
ing then ready to receive the apparatus. The nuts a J and cd cd 
were placed precisely as they had been in Balta; and of course 
the pendulum was effectively of the same length. After the clock 
had been going two days, the semiarc of vibration was observed 
to be 2° 30’; and so it continued till the clock was stopped. 
The transit instrument was placed on a slab of stone half im- 
bedded in sand, as before mentioned. The latitude of the place 
of observation is 51° 28’ 41” north; its altitude 201 feet above 
the level of the sea. 
The “rate” of the clock, as given by observations upon dif- 
ferent stars from day to day, varied between —19 6” and — 20”. 
The mean rate as determined from those stars which presented 
a series of observations upon all the five wires of the transit tele- 
scope, is as below: 
Wt 
: I 
6 Urse majoris, 15 observations,whole loss 2961, mean 19:74 
y Urse majoris, 14 .... soon AO 22.: op teh Os 
¢ Urse majoris, 14 .... eee Lk ei lO-7 
¢ Urse majoris, 14 .... # weieiul2sGn2 « 4) ih 9573 
» Urse majoris, 12 .... bietmaniae att pale. 
x Urse majoris, 2 .... alts TRS: “ere L969 
71 1400-10 
Hence we have 1400:1—71= 19°72, for the mean daily rate 
(—) at Woolwich Common. 
But, as the constant semiare of vibration was less at Balta 
than at Woolwich Common, a correction must be made upon one 
of the rates on that account. Thus, if D=2°f and ¢=2°4, we 
have (Hutton’s Course, vol. iii. p. 358, or Gregory’s Mechanics, 
book ii. chap. 2), 4(D*—2*) = 3(% — 42) = 1342, correction 
to be taken either from the + rate at Balta, or from the — rate 
at Woolwich Common : consequently there results, for 
Balta, N. lat. 60 45 3, alt. ofstation 121 feet, rate + 20°649 
WoolwichCom.51'28 41, . wk ae SOL oe ou, 1972 
The number of: vibrations in a sidereal day being at Balta 
86420°649, at Woolwich 86380-28 ; we have from well-known 
principles 86380°28*; §6420°649?: : 1: 1-00098304. 
Vol, 53, No. 254. June 1819. Ee Such 
