372 



SCIENCE 



[N. S. Vol. L. No. 1294 



first seeing- them, that the men had been dis- 

 charging their excess energy by playing in 

 the snow, and that the balls merely marked 

 the beginning of a snow fort. 



As I approached the parade ground, how- 

 ever, I noted, first, the absence of footprints 

 ill the snow; second, that the paths of the 

 balls were in general parallel, and third, that 

 the " balls " were rolled in one direction only, 

 like cotton batting or a bundle of rugs, and 

 that they were properly speaking " rolls " in- 

 stead of " balls " So I was forced to the con- 

 clusion that they were the effect of the wind. 



On questioning the old inhabitants of the 

 Fort I learned that they were indeed wind- 

 blown, and that such effects occurred not 

 infrequently there. 



The " balls " or " rolls " varied greatly in 

 size. Some were over three feet in diameter, 

 but the majority were smaller, about two feet. 

 The largest 'one that I saw was about four 

 feet in diameter and two feet thick. 



They were all bi-concave. The paths in 

 their wakes were triangular in shape, and 

 varied greatly in length, depending of course 

 on the size of the ball. The path of the large 

 roll mentioned above was over fifty feet in 

 length. 



All the larger balls had fallen on one side, 

 showing that size was not so much a matter 

 of wind-power as it was of balance. 



There were about three inches of soft snow 

 on the ground, and the velocity of the wind 

 was nearly cyclonic. 



Karl M. Dallenbach 



COENELL TJNIVERSITT 



A WALL-SIDE MIRAGE 



To THE Editor op Science: Dr. Knowlton's 

 note on " An unusual mirage " in Science for 

 October 3, suggests mention of a mirage on 

 a vertical north-south wall, on Garden Street, 

 Cambridge, when the warm afternoon sun 

 shines on it in quiet weather. If the ob- 

 server stands close to the plane of the wall, he 

 can easily see a mirror-like reflection of the 

 elbow or of the side profile of a person who is 

 walking near the wall, fifty or a hundred feet 

 away. 



W. M. Davis 



QUOTATIONS 



THE BRITISH ASSOCIATION 



The authorities of the British Association 

 for the Advancement of Science have made 

 known their satisfaction with the meeting at 

 Bournemouth, which ended last Saturday. 

 This judgment doubtless was determined by 

 the old standard, which, even before the war, 

 was neither high nor rising. A warm wel- 

 come from the beautiful town, convenient 

 arrangements for the meetings, summer 

 weather, and nearly 1,500 members, includ- 

 ing quite a number of scientific men, plenty 

 of attractive subjects dealt with by speakers 

 who " drew," and excursions with a decent 

 scientific pretext — such were the materials 

 that produced success. It is to be noticed 

 that they would have suited the requirements 

 of almost any kind of congress. It is more 

 diificult to distinguish in them the " diiler- 

 entia " of a meeting for the advancement of 

 science. Where revelations of the secrets of 

 the war had been promised, there the visitors 

 thronged. The vast growth of naval engines 

 and armaments, hydrophones in fish-like cases, 

 paravanes, sound ranging devices, airships 

 and aeroplanes, tanks and submarine mines, 

 poison gas and high explosives, excited and 

 delighted the members of the British Asso- 

 ciation precisely as they would have excited 

 and delighted the general public. There was 

 a refrain of the achievements of British men 

 of science, as opposed to the vaunted science 

 of Germany, but there was very little of 

 detailed scientific statement or discussion of 

 methods. Almost equally popular were the 

 items in tha Educational Section. Sir 

 Robert Blair on continuation schools. Bishop 

 Welldon on citizenship, General Baden- 

 Powell on the Boy Scout movement, other 

 speakers on the advantages of private schools 

 or the benefits of a sound knowledge of Eng- 

 lish, received and deserved attention. In 

 mentioning a few other examples of the sub- 

 jects that attracted large audiences we throw 

 no doubt on the value of knowledge on the 

 political bearings of international rivers, the 

 use of hypnotism in treating shell-shock, or 

 whether or not the working day should be 



