ON THE METEOROLOGY OP TORONTO IN CANADA, 55 



tively profitless study of the complex effect produced on the barometer by the 

 operation of these two distinct agencies. The labour has been by no means 

 small which has been bestowed in the endeavour to generalise the diurnal 

 phsenomena of the barometer by the formation of empirical formulae ; it has 

 been in many instances the labour of highly accomplished men : but we 

 have the recent acknowledgment of a valued and distinguished member of 

 our own body*, who has himself engaged in this inquiry, that it failed in 

 conducting to a recognition of the causes of the phaenomena. On the other 

 hand, the moment we apply ourselves to the contemplation of the separate 

 phaenomena of the vapour and of the air, there appears to be revealed to 

 us a simple and beautiful dependence of each upon the diurnal march of the 

 temperature, producing effects which in their combination seem also to 

 afford a full and perfect solution of the problem of the daily rise and fall of 

 the barometric column. 



It would be unjust to the meteorologists of Germany if we were not grate- 

 fully to acknowledge in how great a degree this advance in the science is to be 

 ascribed to their writings, and especially to those of M. Dove. Their mete- 

 orological researches have been pressed with an assiduity and devotion of 

 labour which is beyond all praise. In the consideration which we (the mem- 

 bers of the British Association) are likely soon to be called upon to exer- 

 cise, whether any and what great combined endeavours are further desi- 

 rable to be made for the advancement of meteorological science, we should 

 be indeed inexcusable if we neglected to avail ourselves of the advice, and 

 look with becoming respect to the opinions, of men, who have spent yeai's 

 of untiring labour, and brought great attainments to bear, on a branch of 

 science which has been comparatively less cultivated by ourselves. 



Admitting M. Dove's views, we can easily perceive that an empirical for- 

 mula, in which the diurnal oscillation of the barometer should be made to 

 vary as a function of the latitude, could never universally represent the 

 phaenomena. The difference between an insular or littoral station, where 

 the vapour pressure attains its maximum at 9 in the forenoon, and an in- 

 terior station in the same latitude where the maximum is at 2 or 3 in the 

 afternoon, cannot both be represented with fidelity by a formula in which 

 this difference is not taken into the account. At stations where the maxi- 

 mum of vapour pressure takes jDlace at 9 a.m., and the tension thencefor- 

 ward descends until the afternoon, — (as at Trevandrum), — the range of the 

 diurnal oscillation of the barometer will be greater, ceteris paribus, than 

 when, as at Toronto, the vapour pressure progressively rises from sunrise 

 to a maximum at 2 or 3 in the afternoon : the hours of maximum and mi- 

 nimum will also be somewhat modified. 



The important problem of the equality or inequality of the mean press- 

 ure of the gaseous atmosphere at the level of the sea at different points 

 on the surface of the globe, has lately begun to occupy the attention of phy- 

 sical philosophers in a degree which will probably tend, before many years, 

 to its practical solution. In this labour the determinations of our co-operative 

 observatories may perform an important part. Great care has been taken that 

 the barometers of our colonial observatories shall speak precisely the same 

 language as the standard barometer in the Royal Society's Apartments ; and 

 steps are now taking to ensure a similar comparison of the barometers, which, 

 in different parts of the United States, are now observed simultaneously with 

 Toronto by our American coadjutors ; and which may hereafter, if that obser- 

 vatory should be continued, form a very valuable extensive basis of induction 

 for the movements of the atmosphere over that great continent. 



* Professor J. D. Forbes; Meteorological Report. 



