411 
of Edinburgh, Session 1876 - 77 . 
peculiarities of the curve with such completeness as to exhibit 
the variations impressed on the curve by season and by geo- 
graphical position, particularly as regards masses of land and 
extended sheets of water. In low r er latitudes a comparatively 
short time is required ; but even here, where a general regularity 
in the phenomena is perhaps the most striking fact in the meteor- 
ology of equatorial regions, the variations which do occur from 
year to year ought to be carefully observed from their important 
bearing on the whole theory of the movements of the atmosphere. 
The summer months of the northern hemisphere, as regards the 
diurnal oscillations of the barometer, that is the period when 
the influence of the sun is at the maximum as regards its effects 
on these phenomena, are May, June, and July, and the winter 
months, November, December, and January, both corresponding 
with the sun’s declination ; that is, the effects are not cumulative, 
as in the case of the temperature of the air or that of the sea, by 
which the critical periods are retarded from one to two months. 
Among the many interesting features of the curves which were 
pointed out may be noted the enormous influence of latitude and 
of land and sea respectively in determining the amount and time 
of occurrence of the different phases of the oscillations, and a 
diagram was exhibited showing the curves of a large number of 
places, from which it appeared that as regards the summer the a.ri. 
maximum occurs at any time from 6-7 a.m. to 2 p.m., and the p.m. 
minimum from 3 to 8 p.m. — the stations selected showing a regular 
gradation between these extremes, a gradation dependent on geo- 
graphical position. The tendency of assimilation of the curves for 
certain elevated stations and those for strictly sea-side stations was 
pointed out, and attention was drawn to the striking fact that the 
summer curves of inland stations within lat. 30° N. and S. essen- 
tially differed from those of higher latitudes — a difference which 
the varying declination of the sun with season failed to obliterate. 
An examination of the different theories yet propounded shows 
that none of them are in accordance with the facts which have 
been collected. It would not be difficult by a proper selection of 
stations to bring proof in support of any of these theories. The 
truth is, however, that as more facts are obtained the difficulty of 
framing a satisfactory theory can scarcely be said to be materially 
