138 THE ROYAL SOCIETY OF CANADA 



brought in for the purpose of obtaining a more reliable final mean than 

 would be got from only one method, rather than to show any relation- 

 ship between the two means. 



Comparing the mean gust velocity calculated from the max. 

 readings (viz. 24-2 mis/hr)and the mean lull velocity calculated from 

 the min. readings (viz. 12-5 mis/hr) with the mean of the Rob. Cup 

 readings (viz. 19-6 mis/hr) for the corresponding periods, we get for 

 the duration of our test that the mean gust velocity was equal to 

 1-23 V, and that the mean lull velocity was equal to 0-65 v, where v 

 is the mean velocity determined from the standardized cups. The 

 extreme gust velocity was 1-4 v and the extreme lull velocity (with 

 the exception of the exceptional observation No. 11) was 0-60 v.^ 

 These two latter values are probably too great because no correction 

 has been made for the vibration of the gasoline, which would certainly 

 augment the extreme readings. 



Considering the fact that no recording or damping device was 

 introduced, the general consistency of the figures in the table is per- 

 haps more remarkable than is at first apparent. It should be noted 

 that the probable error for a single mean by either method amounts 

 to much less than 1 mile per hour in the calculated velocity. The 

 extreme difference obtained in the unexplained variation of observa- 

 tion No. 11, amounts to 3 mis/hr. and there were only two other cases 

 where the difference amounted to 2 mis/hr. In other tests the mean 

 values for the wind were in complete agreement for several types of 

 instrument. 



These Tubes were used for recording the number of the gusts in 

 a given period very successfully, as well as their range in velocity. 

 A summary of some results obtained in this way, is given by Mr. J. Pat- 

 terson and the present writer in a section of Dr. L. V. King's Report.^ 

 Checks were made on this method of indicating the frequency of gusts 

 or double fluctuations of pressure (1) by watching the behaviour of a 

 small tethered pilot balloon, (2) by comparing with the record of a 

 Dines Microborograph, and (3) by counting the successive dark 

 regions which were caused on the surface of the water on a day when 

 the gustiness was very marked. A fair agreement was obtained. 



The writer desires to express again his thanks to Dr. L. V. King 

 for the opportunity to perform these tests during the main work of 

 the party at Father Point, and to Mr. J. Patterson for his valuable 

 directions. 



Macdonald College, McGill University. 



^Compare these four values with the results (1-2 v, 0-75 v, 1-3 v, and 0-65 v 

 respectively) given by W. N. Shaw, in Report of the Adv. Com. for Aeronautics {Brit.), 

 1909-10, p. 97; also G. C. Simpson in M.D. Pub. 180, p. 37. 



^Loc. cit. 



