﻿348 Transactions — Miscellaneous. 



cate a subject in which no great accuracy was to be expected, I omitted the 

 resistance of the air to the under surface of the body of the bird as being 

 very small in comparison to that of the wings. 



Witli tliese explanations I will now proceed to discuss the appendix to 

 Mr. Webb's paper. 



Page 234, line 4 from bottom, et seq. — " Captain Hiitton first assumes 

 that the number of feet the bird travels in one second = HE, and then that 

 the bird will pass in the same time through the longer distance AE." 



Mr. Webb has here fallen into a mistake through not having comprehended 

 my meaning, which may not, perhaps, have been very clearly expressed. 

 HE represents the actual velocity of the bird, and is the only line that could 

 be determined by observation. AE represents the distance it would have 

 passed through but for the counteracting influence of gravity, and must be 

 calculated from HE. 



Page 234, line 2 from bottom, et seq. — " The mistake leads him (Capt. H.) 

 to the fux'ther error of adopting HE tan AEH as the measure of the vertical 

 component of the atmosjoheric resistance instead of HE sin AEH." 



Mx\ Webb has again failed to comprehend my meaning, but this time from 

 carelessness in reading my paper. AH is not taken by me to represent the 

 height the bird would rise by atmospheric resistance, but by the direction in 

 which the bird was flying — viz., slightly upwards ; and this inattention has led 

 him into the remark that I have " unaccountably adopted a totally diflerent 

 method to arrive at the vertical component of resistance in the case of the 

 wings," the truth being that I have adoj)ted " totally different methods " for 

 dealing with two totally diflerent things— viz., the angle of flight in the first 

 case, and the resistance of the air to the wings of the bird in the second. It 

 will, therefore, be seen that it is not I, but Mr Webb, who has arrived at the 

 " strange conclusion " mentioned a few lines further on. Even if it had been 

 the atmospheric resistance that was here being considered, HE sin AEH would 

 not be the measure of the vertical component, for it is the measure of the 

 whole of the resistance both to forward as well as to downward movement. 



Page 235, line 16. — -"The whole force exerted by the bird is, in fact, 

 HE + P." I do not know what Mr. Webb means by this, for HE does not 

 represent a force at all, but the velocity of the bird, Avhich is a very diflerent 

 thing, although it will, no doubt, have a cei'tain ratio to the force exerted by 

 the bird. 



Page 235, lines 17-18.— "It is not LE but KE ( = HE sin CEH) which 

 represents the vertical component of the force actually at work." 



How KE can be supposed to represent the vertical component of any 

 force is more than I can understand. It is the same error as that pre- 

 viously made with regard to HE sin AEH. 



