^N'ov. 1890.] 



AKD OOLOGIST. 



165 



The followiiij;- officers were elected for the 

 foUowins year: Presiileut, Amos W. Butler, 

 Brookvilie, Iiul.; secretary, Prof. Charles 

 \V. Ilargitt, Oxford, Ohio; treasurer, Otto 

 Widmanii, Old Orchard, Mo. 



Aiiotlier ineetini; \vill be held in connection 

 with that of the A. A. A. S. at AVashington, 

 D. C, next year. The secretary will be glad 

 to have any suggestions or answer any in- 

 <iuiries from those interested in the work of 

 the association. 



Preliminary articles of association were 

 presented by the committee. These will be 

 extended and modified as occasion may require. 



Tiie present idea seems to be that the asso- 

 ciation should be accessory to the American 

 association; a sort of ^'- . sectional club.'''' 



Cha.s. IV. Ilnrgiff, Sec. 



.AIi;,mi riiiver.-ity, Oxford, Ohio, Oct. 25, 1890. 



The Capacity of Eggs. 



Nesting of the Prairie Warbler at 

 Raleigh, N. C. 



In a former article 1 suggested .208 as a con- 

 stant l)y which the cube of the length of an 

 egg may be multiplied in order to determine 

 its capacity in cubic inches. A further study 

 of the subject seems to show this to be really 

 of more practical value than a formula which 

 gives due weight to the width of the egg as 

 well as its length. I must own that this result 

 was directly the reverse of my own opinion 

 before testing the matter in a practical way. 

 Though observations, when all known instru- 

 luental errors have been expunged, are of 

 more value than computation, the human mind 

 is apt to be strongly biased in favor of the 

 latter. If others see any points that I have 

 missed I hope to hear from them through the 

 pages of the O. & O. 



In i)reparing the accompanying table the fol- 

 lowing formulai have been used: 



The Prairie Waibler {Bendroiai discolor) is 

 fairly common at Ilaleigh, but the nest is by 

 no means easy to find as the birds seem to 

 wander, while Ituilding, (juite a long way from 

 tlie nest, and even when the nest is found it is 

 often deserted afterwards, so sets don't get 

 taken as often as it looks as if they ought. 



In tills locality the Prairie Warbler delights 

 in sunny hillsides covered with bushes and 

 saplings, building its nest in one of these at a 

 height of from one to twelve feet from the 

 ground, but usually about three or four feet 

 high. They start building about tiie first of 

 May and uill have fresh sets from the middle 

 to tiie end of May, some pairs being later than 

 others, apparently. The nest is a beautiful 

 structure, usually being largely comi)osed of 

 rabbit tobacco, a kind of gray-leaved, wild ever- 

 lasting very much used by birds in nest build- 

 ing, and is lined with soft materials. 



Unlike some localities where this bird nests 

 mainly in pine saplings, here sweet gums are 

 the preference, with elm about next best, 

 nests being only found very occasionally in 

 pines, although ])ine saplings about the right 

 size are usually more abundant in the locali- 

 ties frequented by this liird than any other 

 tree. 



The set is usuiUly four, sometimes three, and 

 if one set is taken another nest will be built 

 and another set laid, but the second nest is 

 usually harder to find than the first, and that 

 is hard enough. C. S. Bfimley. 



Uuleifili. X. C. 



a = the length of the egg. 

 h -= the breadth of the egg. 



1) a" X .2(18 = capacity of an "ideal egg" as de- 

 termined in the article above referred to. 



(Jrx«x4.i9 



old. 



capacity of a prolate spher- 



This is the formula which I expected would 

 give results more closely in accordance with 

 observations (/.e., determinations of capacity 

 by weighing) than I could possibly do. Find- 

 ing it less accurate when the mean percentage 

 of variation was computed as a test I had 

 recourse to 



?y) }y' X.2G18 -h (J)'x (a — -) X 2.094. 



This formula is based on the assumption 

 that the large end of an egg is half of a sphere 

 and the small end half of a prolate spheroid. 

 In the following table, for the basis of calcula- 

 tion I have used the measurement of eggs 

 given in EitJ(jiccu/s Manual of North American 

 Birds. They are undoubtedly more accurate 

 than any which I could make with the instru- 

 ments which I have at hand, and I consider 

 them as a perfectly good scientific standard. 

 The next column shows the capacity in cubic 

 inches of some of the eggs which I computed 

 from their weight when filled with shot. I 

 would like to have had these results checked 

 by an independent observer, but to ensure all 

 possil)le accuracy I have omitted all which 

 were not based upon the weight of five (-5) or 



