406 ALEXANDER BUCHAN ON THE 
It follows that the minimum deflection occurs at the season of the year 
when the earth presents the minimum extent of land, in other words, the most 
uniform surface, to the perpendicular rays of the sun ; and the maximum deflec- 
tion occurs at the season when the earth presents the maximum extent of land, 
in other words, the most varied surface, to the sun. Beyond this broad 
generalisation of the facts of distribution of this oscillation, we are scarcely 
warranted to go at this stage of the discussion. While, as has been pointed out, 
numerous illustrations can be adduced showing a larger oscillation over the 
same region with a high temperature and a dry atmosphere, than with a low 
temperature and a moist atmosphere, the small summer oscillation on the 
coasts of the Mediterranean and those of the Atlantic adjoining, is in direct 
opposition to the idea that any such conclusion is general. For over these parts 
of the Mediterranean and Atlantic the temperature is hottest In summer and 
the air is driest, so dry indeed that no rain or next to none falls, and yet there 
the amplitude of the oscillation now contracts to its annual minimum. On the 
western coasts of the Atlantic, from the Bahamas northwards to Newfoundland, 
the temperature is at the annual maximum, but the air is not dry, being liberally 
supplied with moisture, and the rainfall is generous. But with these very dif- 
ferent meteorological conditions, there occurs equally, as in southern Europe, 
a diminished oscillation during the summer months in the islands and near the 
coasts of North America. It is also to be noted that at inland situations both 
in America and in the south of Europe, the oscillation reaches its annual — 
maximum just at this season when the annual minimum occurs near the sea- _ 
coasts, even although the general characteristics of the atmosphere be substan- 
tially the same in both cases. 
Hence, then, it is not merely latitude and the states of the atmosphere 
which call for consideration in this inquiry, but it is these, combined with the 
effects of solar and terrestrial radiation, of currents of air, and possibly also 
of electro-magnetic conditions, as modified in each locality by the relative 
distribution of land and water. The development of this question would 
be most materially furthered by establishing in different parts of the globe 
strings of stations extending from the sea-shore inland for thirty or forty miles ; 
and, it may be added, that with observations obtained from stations so planted, 
the investigation of the important question of sea-side and other local climates 
would be most satisfactorily carried out, since it would thereby be placed on a 
strictly scientific basis. 
In Part II. it is proposed to discuss by the usual mathematical formule, 
the mean hourly and bi-hourly observations which have been collected from 
eighty-six stations, with the view of approximately determining the exact time 
of occurrence and the amount of the two daily maxima and minima of each 
month, and the time of occurrence of the four daily mean values. 

