307 
of Edinburgh, Session 1867-68. 
is the region of low pressure round the south pole, which probably 
is subject to little variation throughout the year. The depression in 
the neighbourhood of the north pole is divided into distinct centres, 
at each of which a diminution of pressure still further below the 
average pressure prevails. These are the north part of the Atlantic 
and the north part of the Pacific oceans. There is also a smaller 
area of low pressure in Hindustan, caused altogether by the low 
summer pressure of that region during the south-west monsoon. The 
centre of Asia is also a little below the average, owing to the very 
low summer pressure. 
These differences in the pressure arise from the unequal distribu- 
tion either of the temperature or of the moisture of the atmosphere* 
Of these, considered as disturbing agents, by far the most important 
is the moisture, — thus giving to this element a paramount claim on 
our regard in studying winds, storms, and other atmospheric changes. 
The relations of the barometric pressure to the prevailing winds, 
the varying temperature, and the rainfall in different parts of the 
world, were pointed out. Isobarometric and isothermal charts,— 
(1.) Of Europe and Western Asia, from the 18th to the 26th of 
December 1866 ; and (2.) Of Europe, from the 19th July to the 1st 
of August 1867, were exhibited ; and it was shown that the remark- 
able deviations from the mean pressure of these months which then 
prevailed were accompanied with equally remarkable deviations 
from the mean temperature of the same months. 
2. On the History of the Sun’s Distance Determinations ; 
and on Scriptural and Scientific Probabilities. By William 
Petrie, Esq. Communicated by Professor C. Piazzi Smyth, 
March 16, 1868. 
This paper was accompanied by two diagrams, one of them repre- 
senting more particularly the features attending on space, and the 
probable errors of several modern determinations therein ; and the 
other representing the chronological order of the events, or progress 
made by man from the earliest times, down to the present, in ascer- 
taining that most important of all questions in astronomy and gene- 
ral physics, viz., the true mean distance of the earth from the sun. 
At the dawn of human science, properly so called, or of efforts 
