58 LOCAL VARIATIONS AND VIBRATIONS OF EARTH’S SURFACE. 
at the gauge ; and to make such a change, a strong southerly gale 
of wind would be required blowing on the south end of the lake, 
near where the gauge is, whi ch could not have been the case 
without ot i knowing g it. 
There n the instrumental corrections of the 
Sydney Pieter pase uibk this lake change on July 28, nor 
any circumstances of lunar position which might be suppos 
be connected with it. Here, for the present, I must leave these 
lake changes, only remarking that the record referred to above 
was made subsequent to the reading of this paper, but before the 
proof was corrected, and I have used it as a better example than 
that “i at the meeting. 
e I leave this part of my subject I would like to call your 
Sitenkicn to the fact that the lake is most disturbed when the 
barometer is low, which accords with the results of seismic obser- 
vations in Italy and other places. You may remember that in my 
address, read in May, I expressed the opinion that the greater dis 
turbance with a low barometer was not because the barometer was 
on the earth which sets it into vibration in the same way as it 
does the sea. 
The statement made by M. Plantamour that in Europe the 
eastern piers of transit instruments rise in summer and fall in 
view that it should be proved or disproved at once, and I 
therefore wish to contribute the results = our experience towards 
the discussion of this question, for it is only by collecting the 
results from a great number of vteealoren that this can be 
late Mr, Smalley, all the then existing azimuth observations in 
Sydney, and four years of Greenwich results, for a paper which 
he read to this Society on “the azimuthal changes of hills.” Ever 
since I have been very much a ong in the question. At 
the time I refer to, and for some years after, we had at 
Sydney one of those ola fashioned inten sisbies with the telescope 
circle near one pier; an example of the gradual change 
by which we got from the old mural circle to the symmetrical 
modern transit instrument. Ours was made up of cast and ham- 
mered brass, in just so many pieces as suited the workman’s con- 
venience, and these, put together under the then existing idea of 
what was best or most convenient to make, resulted in an instru- 
ment which, viewed in the light of present practice, seems to have 
