42 Dr. Ballot on the importance of Deviation sfrom the mea?i 



I do not feel myself competent to express a decided opinion 

 upon this "vexed question;" but regarding the lake theory 

 as the true one, I think it now only remains to be determined 

 whether the barriers at the mouths of the glens consisted of 

 ice or of earthy materials. Perhaps we know nearly as much 

 regarding the latter as we ever can know; but the valley of 

 the Spean has never been carefully examined, with reference 

 to the former passage of glaciers through it, by one fully com- 

 petent to the task. Till this has been done, geologists are 

 not in a position to decide between the rival theories. 



Ill, On the great importance of Deviations from the mean 

 state of the Atmosphere for the Science of Meteorology. By 

 Dr. Buys Ballot*. 



THERE are some points in meteorology which certainly 

 are no longer disputed, but which nevertheless are not 

 always sufficiently present to the minds of meteorologists, nor 

 so publicly pronounced and admitted as to compel them to 

 action, and serve as a torch to illumine the path leading to 

 the penetralia of science. Though these facts may appear 

 simple, particularly in England, where they have been treated 

 upon, still even there it cannot be considered superfluous to 

 view them in another light, and to introduce them in connexion 

 with a Dutch prize question, which, in my opinion, is the 

 most important meteorological question that can be brought 

 forward, and which fully characterizes the new meteorological 

 period developed by Dove. 



On the other hand, England has such boundless merits as 

 to meteorological observations, and has such great facilities, 

 in consequence of her extensive influence and wide-spread 

 observatories, for the application of those facts in all parts 

 of the earth, that she has a right to receive information, 

 through her own periodicals, of what is taking place on the 

 continent. I therefore decided (on being solicited by the 

 Society of Physics of Berlin to send in annually a report of, 

 and opinions on, what might occur in meteorology) to adopt 

 also for insertion in an English periodical, by modifying some 

 points of less interest, a paper drawn up for the Journal of 

 the Society, Die Fortschritte der Physik. The truths to which 

 1 allude were particularly remarked by me in 184-6, when I 

 wrote my work Les Changements Periodiques de Temperature 

 dependants de la nature du Soleil et de la Lune deduits d? ob- 

 servations Neerlandaises de 1729-1846, in which those parti- 



* Communicated by the Astronomer Royal. 



