THE BRITISH ASSOCIATION AT MONTREAL. 305 



whereas in the north frozen ground in certain districts, as in Siberia and North- 

 western Canada, extends beyond the fiftieth parallel f therefore by comparison 

 the north, as regards the latitude in which Great Britain is situated, is at presen 

 the most glacial hemisphere. As it is very difficult to conceive that the earth 

 had at any former period a lower initial temperature, or that the sun possessed 

 less heating power, glaciation in the north could never have depended upon the 

 conditions argued in Dr. Croll's theory. The author suggested that glaciation 

 within latitudes 40° and 60° was probably at all periods a local phenomenon, de- 

 pending upon the direction taken by aerial and oceanic currents, as, for instance, 

 Greenland is at present being glaciated. Norway has a mild chmate in the same 

 latitude, the one being situated in the predominating Northern Atlantic currents, 

 the other in the southern. Certain physical changes suggested in the distribution 

 of land would reverse these conditions and render Greenland the warmer climate, 

 Norway the colder." 



In regard to sunspots and terrestrial disturbances. Prof. Arthur Schuster, of 

 Owens College, Manchester, said their periodicity was not regular. Sometimes 

 they appear every eight years, and sometimes not for sixteen years. The period 

 is about every eleven years. There is ground for believing that there are two 

 periods often and a half and twelve years superposed on one another. Magnetic 

 variations, that is, variations of the magnetic needle, occur at such times, which 

 are quite marked. The magnetic needle points to the north and the south. It 

 does this, however, approximately, and follows the course of the sun somewhat. 

 In the mornin'g it begins traveling westward, and in the afternoon it starts on its 

 run to where it began. This daily excursion of the needle is much greater when 

 there are many spots on the sun. The proportion in England is as three to two, 

 and in Germany as seven to four. At times, too, the needle travels irregularly 

 to and fro. These needle vibrations are magnetic storms. The speaker referred 

 to the noted storms of 1859 and 1872, at the time of great outbursts on the sun, 

 and said that if the sun were of solid steel, magnetized to the highest extent 

 of which it is capable, it would not affect terrestrial phenomena to such an extent, 

 It was rash to say that the space between the earth and the sun did not contain 

 sufficient matter to conduct electricity from one to the other, but leaving electric 

 influence out of the matter, because we know nothing of the subject, we come to 

 the question, '^ Does the sun radiate more or less at the time of the prevalence of 

 sunspots?" This was not definitely ascertained. The trouble has been in try- 

 ing to ascertain the sun's radiant heat, and we have not been able to get rid of 

 disturbing factors, one of which is the variance in the absorption, reflection, etc. 

 in the atmosphere at different times of the day. Prof. Schuster suggested the es- 

 tablishment of an observatory station on Himalaya Mountains, about 20,000 feet 

 above the level of the sea. He then pointed out the difficulties in the way of 

 determining the solar heat, and called attention to the thermic curves. During 

 the period between 18 10 and i860 there was a remarkable correspondence be- 

 tween the mean temperature curves and the prevalence of sun spots in unusual 

 numbers. The good wine years on the Rhine correspond with the years of mini- 



