PROCEEDINGS OF SECTION E. 279 
cherished idea, and a cellar of sufficient size and lght was 
selected for the room for erecting the apparatus, the descrip- 
tion of which I am about to give. 
Before entering upon this it will be necessary to give some 
particulars of the 
PosITION OF THE PENDULUM Room. 
The distance of this place from the transit-room of the new 
observatory is 1340 ft., and the bearing from the latter towards 
it is S. 36 deg. 30 min. E.; from this, and the position of the 
transit-room, the geographical position was found to be in 
37 deg. 50 min. 4 sec. south latitude and 9 hr. 39 min. 55.4 sec. 
east longitude. From a series of corresponding barometer 
readings made in the transit-room and in the cellar, it would 
appear that the cistern of the standard barometer in the former 
is 34.5 ft. above the lower arm of the syphon standard baro- 
meter in the latter, and as the elevation above the mean level 
of the sea of the barometer at the observatory is 91.3 ft., the 
elevation of the syphon barometer is 56.8 ft. The floor of the 
room is about 6 ft. below the level of Domain-road, in which 
the buildings are situated. The room selected is one of two of 
nearly the same size, viz., 18 ft. by 12ft., and although the 
southernmost would have been farther from the road, and less 
likely to be disturbed by passing vehicles, I preferred to take 
the one towards north, as in this case I had less difficulty to 
arrange the apparatus than in the other room, in which the 
staircase takes away much room and made a protection against 
sudden changes in temperature of air less efficient. A series of 
observations, made with a view to determine the extent to 
which vibrations from vehicles are communicated to the place 
of observation, convinced me that I had little to fear from such 
disturbing causes; the less so, as it was in my power to make 
the observations at such hours of the day when hardly any 
vehicles passed the place, and as the rate of the clock could be 
continually controlled by chronographical registrations at the 
new observatory. 
PREPARING THE Room FOR THE RECEPTION OF THE 
APPARATUS. 
The small height of the room required the devising of means 
to make it available for the purpose. As the whole height of 
7 ft. 7 in. exceeded the length of the pendulum of 7 ft. 2.2 in. 
by only 4.8 in., I had to make an excavation which would 
admit of an observer being seated at a telescope, the eye on 
a level with the lower end of the pendulum, and which had to 
be large enough at the same time to receive the clock. It 
was therefore made 11 ft. 10 in. by 3 ft. 5 in., its depth being 
