Annual Report of the i>. A. Institution. ] 19 



tion of every breeze which has breathed upon the ocean. .We 

 would earnestly recommend the collection of such journals, to 

 all members of the Institution who have opportunity. 



We have our own part also in these discoveries to fulfil ; 

 the importanco of which part will be evinced by a slight con- 

 sideration of our position. All great changes in the aerial 

 currents must be dependant on the universal currents, to which 

 the atmosphere enveloping the world is subjected. Of these 

 currents, the one sweeps over us in summer, diffusing the 

 coolness of the higher latitudes over the regions betwixt us and 

 the equator; it directs its course upon the warm and humid 

 countries of tho tro.pics, to which it is attracted by the influence 

 of a vertical sun, expanding and raising the stream as it arrives 

 loaded with the heat and vapour of the tropic atmosphere. — 

 As it cannot be sustained in a heap over the equator, it neces- 

 sarily flows back ; constituting an upper stream sliding across 

 the lower sheet of cooler air which supplies it, and it proceeds 

 to its origin again, falling down upon the higher latitudes, and 

 imparting to them the moisture of the equatorial seas and 

 marshes. In the northern hemisphere, it forms the humid 

 zephyr which breathes along with the moistures, somewhat of 

 the heat of the central regions, over the cooler latitudes, where 

 it falls. 



In our position we encounter it us the rainy north-wester, 

 rendered comparatively cold by its long journey in the high 

 and freezing regions which it traverses. Various causes pro- 

 duce irregularities in the boundaries of that region or belt.over 

 which these currents pass, and more particularly on that verge 

 of the belt where tho one stream commences its direction 

 towards the equator and the other decends to fill the void. 

 There the currents must be found intermingling, changing their 

 relative positions, and each influencing in all imaginable 

 modes and degrees, the direction and energy of the other, 



Upon this boundary are we situated, or rather, it may be said, 

 to pass over our heads in the transition from one season to the 

 other. In following the parallel of latitude in which we are, 

 we shall probably find places which are more permanently 

 within, and others more permanently excluded from this 

 boundary. Tho curves which the boundary would thus trace 

 upon the globe, must be constantly varying their position and 

 inflexions, not only in the changing seasons of any one year, 

 but also in tho corresponding seasons of one as compared with 

 another. Since nothing new starts into being amidst the 

 material causes of these changes, and nothing escapes that 

 we know of by which they are much influenced, their varieties 

 doubtless arc subject to laws, intended for man's observation 



