176 PROCEEDINGS OF THE ACADEMY OF 



was at Montreal, either the same summer or in that of 1858, when I spent 

 more than a month in or near that city. That difference of latitude, about 

 three degrees, made what appeared to me a disproportionate difference in the 

 frequency of auroral displajs, — a difference, however, not as great as that be- 

 tween Montreal and Philadelphia, which is again a difference of latitude about 

 five and a half degrees. 



In high northern latitudes the auroral phenomena are rendered invisible a 

 very large part of the year by twilight. At Montreal the twilight lasts until 

 10 o'clock and begins at 2 ; and on the Saguenay it ends at 11 o'clock and 

 begins at 1. In latitude near 60° N. many jears ago, in the month of June, I 

 could read very easily at midnight by the light of the sun, which luminary 

 seemed, by his bright rosy reflections against the clouds, to be but very little 

 below the northern horizon. Plainly there can be but little chance for the 

 electric aurora to shine among the rosy fingers of the due northern solar 

 aurora. As in those regions the electric process causing the aurora occurs 

 almost every night when there is little or no twilight, so we may presume the 

 same process continues when a strong twilight hides the boreal aurora, espe- 

 cially since we know that auroras may be indicated by the magneiic needle 

 when they are not actually visible to the eye. Our present reports from the 

 far north lead to the supposition that the auroral process is more frequent on 

 some meridians of longitude than on others, and that it is effected by geogra- 

 phical causes. Probably also many reporters, being exploring travellers and 

 not scientific observers, have thought the fainter and less conspicuous auroras 

 unworthy of record ; and hence Prof. Loomis' small number of eighty per 

 annum for the maximum average in any zone. 



Both Capt. Franklin and Dr. Richardson testify that "the auroral pheno-- 

 mena are frequently seated within the region of the clouds." Hood states that 

 he saw the aurora several times only six or seven miles above the earth's 

 surface; among others, on Oct. 23, 1819, and June 13, 1820. I have observed 

 similar cases. All the facts agree best with the idea that the liberation of the 

 electricity causing the aurora takes place daily within the atmosphere, and 

 that thence it escapes southerly by the three paths I have mentioned. The 

 constant flow of electricity from the north requires in that region a constant 

 supply. This supply must be afforded by the constant flow of the atmosphere 

 to the north from the equatorial regions, where at its very start it is charged 

 with electricity by simple evaporation from the saline waters of the oceans. 

 For it is a well known fact that positive electricity abounds in all vapors from 

 waters only slightly saline. It has long been remarked that terrestrial mag- 

 netism and atmospheric electricity seem intimately connected. They cannot 

 depend on geological causes, for we see nothing in the mineral constitution 

 of the globe to produce such variable phenomena. They must depend on the 

 radiations from the sun, either directly in part by changes of temperature, as 

 Faraday thought, or indirectly by some other means, such as evaporation, 

 condensation, friction of atmospheric strata, and the like. Mysterious as the 

 whole subject now appears, it is nevertheless plainly a soluble question, and 

 awaits only the coming man armed fully with physical and meteorological 

 science, and having patience to give the problem a few years of undivided 

 attention. 



On the production of BEACTEA in LARIX. 



BY THOMAS MEEHAN. 



I have no desire to press with undue force on my fellow-students in Bota- 

 ny the importance of the discovery I made last year, that many of the great 

 differences we see in varieties, species or even genera in Uonifera-, are 

 resolvable into the simple question of axial vigor ; but the key it furnished 

 enables me frequently to unlock some heretofore secret and mysterious 



[Atigust 



