6i8 



NA TURE 



{Oct. 23, 1 1 



Dr. Leonhard Stejneger exhibited a stuffed specimen of a 

 willow grouse from Newfoundland, which he regarded as a new 

 geographical race, differing from the continental form chiefly in 

 the possession of more or less black upon its primaries. Mr. 

 Brewster said that he had recently examined 150 specimens of 

 ptarmigan from Newfoundland, and hail observed the peculiari- 

 ties pointed out, but did not consider them constant, lie was 

 inclined to regard the characters mentioned as seasonal, and 

 possibly to some extent individual. Dr. Stejneger replied that 

 this coloration of the wing feathers could not possibly be 

 seasonal as they (the primaries) were moulted but once a year. 

 Dr. Merriam stated that during a recent visit to Newfoundland 

 he had examined a very large number of willow grouse in the 

 flesh, and was still engaged in investigating the change of colour 

 in this species. His studies led him to disagree with Dr. 

 Stejneger's last statement. He (Dr. Merriam) was convinced 

 that change in colour in individual feathers did take place, both 

 independent of and coincident with the moult. Mr. D. G. 

 Elliot agreed with Mr. Merriam in considering the change of 

 colour of individual feathers an established fact. An animated 

 discussion followed, and was participated in by Messrs. Brewster, 

 Comeau, Coues, Elliot, Merriam, Ridgway, and Stejneger. 



In response to a call from the President, Dr. P. L. Sclater 

 said : — 



"I hope the members of the American Ornithologists' Union 

 will excuse me if I offend the feelings of any one by the remarks I 

 am about to make. It has aggrieved me much to find in this 

 country three large and valuable collections of birds which are 

 not under the care of paid working ornithologists. One of these 

 is in Boston, one in New York, and the other in Philadelphia. 

 Each contains what all ornithologists admit to be most valuable 

 typical specimens. A grave responsibility rests upon the pos- 

 sessors of types of species, and the loss or injury of such specimens 

 is a great and irreparable loss to science. The collection of the 

 Boston Society of Natural History (known as the La Frenaye 

 Collection) has been much damaged by neglect, and the entire 

 collection ought to be catalogued and so arranged as to render 

 any particular specimen readily accessible. In this building (the 

 American Museum of Natural History in New York) are the 

 types of the celebrated Maximilian Collection, and many other 

 specimens of exceeding great value. A large number of these 

 have never been properly identified, and some of them are 

 missing and have doubtless been destroyed by insect pests. The 

 value of others has been lost through neglect, by the displace- 

 ment of labels, and by the omission of proper measures for their 

 preservation. The same remarks would, in a general way, 

 apply to the collections of the Philadelphia Academy of Natural 

 Sciences. It is sad to find no paid ornithologists in charge of 

 these exceedingly valuable collections, and I beg to suggest that 

 the American Ornithologists' Union can undertake no worthier 

 task than to impress upon the proper authorities the urgent 

 necessity of immediate action in this matter.'' 



The officers of the Union were re-elected as follows : — Pre- 

 sident, J. A. Allen, Cambridge; Vice-President.-,, Dr. Elliott 

 Cones and Robert Ridgway, Washington ; Secretary and Trea- 

 surer, Dr. C. Hart Merriam, Locust Grove, New York. 



The place of meeting for next year was referred to the Council 

 for decision. 



THE CAPILLARY CONSTANTS OF LLOUIDS 

 AT THELR BOILING-POINTS ~ 

 'T'HE paper of Prof. Robert Scruff, published in Liebig's 

 Annalen, March 1884, on this subject, marks the first 

 successful attempt out of many that have been made to com;, . 

 the surface-tension of a liquid with its molecular constitution. 



It has long been known that the tension diminishes rapidly 

 with a rise of temperature, but the importance of this fact when 

 it is desired to make a comparative examination of different 

 liquids has not been fully appreciated or sufficiently insisted on 

 till now by Prof. Schiff, who has to lament that, out of the 

 considerable array of experimental investigations on the subject 

 which he has examined, very few results could be extracted which 

 could be usefully employed in such a comparative study, a failure 

 which he attributes to the completely arbitrary and dissimilar 

 physical conditions under which the different substances in 

 question have been examined. 



Since it is impossible to compare surface-tensions at the critical 

 point, because that is the point at which the surface-tension 

 vanishes, it is necessary to seek some other condition in which 



different liquids may be physically comparable, and that whicr 

 naturally suggested itself for trial to Prof. Schiff, was the boiling- 

 point of the liquid itself, whose significance in this respect he 

 has himself established. 



The principle of his method was to select with great care two 

 capillary glass tubes of perfectly cylindrical bore, but of different 

 diameters, that of the wider being about I '3 mm., and of the 

 narrower about half as much. These two tubes are then united 

 into a little Utube (about 7 cm. long), which, after being partly 

 filled with the experimental liquid, is hung in a wider vessel, at 

 the bottom of which a little of the same liquid is kept boiling. 

 From the difference of level of the liquid in these two con- 

 nected capillary tubes, as measured at a temperature which must 

 be very nearly the boiling-point, the surface-tension at that tem- 

 perature is readily deduced, since the method of procedure in- 

 volves the thorough wetting of the upper portion of the tube with 

 condensed liquid. 



In this manner Prof. Schiff has determined the surface-tension 

 at the boiling-point of some sixty liquids, with a possible error 

 which he estimates at 175 per cent, of the mean value — at the 

 worst, 2 '4 per cent. His results may be stated as follows : — 



1. For isomeric liquids that are chemically comparable, the 

 surface-tension at the boiling-point is the same (within the limits 

 of observational error). The observations do indeed point in 

 the case of isomers of one class to a fall in surface-tension with 

 a fall in the boiling-point, while in another class there is a per- 

 ceptible rise with a rise in the boiling-point, but these variations 

 are within the limits of possible errors of observation. 



2. The quantity which turns out to be that on which attention 

 should be fixed is not the surface-tension itself, but the surface- 

 tension divided by the molecular weight, a quantity to which 

 the author gives a vivid significance by pointing out that, in the 

 case of a capillary elevation against a vertical wall wetted by the 

 liquid, it is proportional to and represents the number of molecules 

 raised above the free surface per unit length of the wall; for, 

 since the tension per unit length is equal to the weight of the 

 total number of molecules lifted, this tension divided by the 

 weight of each molecule gives the total number lifted. 



To the surface-tension in milligrams per millimetre divided by 

 the relative molecular weight (and multiplied for convenience by 

 1000), Prof. Schiff accordingly assigns the symbol N, and his re- 

 sults show that not only is this number N the same for isomeric 

 substances (as is implied in the previous statement), but that it is 

 often the same for liquids of very different chemical constitution. 

 He then proceeds to examine the formula? of such chemically 

 different liquids which have the common property that N is the 

 same, in the manner exemplified in the following illustration : — 



" Taking all the different substances for which N is nearly 

 16, we find — 



Hexane, C G H 14 N 



Xylol, ethyl-benzol, C 8 H in ... 



i6-i 

 160 



1 15-9 

 15-8 



I, 16-2 



I5-S 



156 



With the formula C 5 H J0 O, ... N = 15-6 



I I5'9 

 157 



" This indicates that substances with the formulae 

 C 6 H 14 , C 8 H ]0 , C 5 H l0 O 2 , 



are, so far as concerns the value of the number (N) of mole- 

 cules lifted, equivalent to each other. 



"C 6 H U differs from C 8 H 10 in having C s less and H4 more ; 

 accordingly, so far as concerns the constant N, 

 2C = 4 H. 



" C 8 H U1 differs from C 5 H, O 2 in having C 3 more and 0„ less, 

 so that, with reference to the constant N, 

 3C = 2O." 



In order to test whether these equivalences are accidental or 

 not, he examines other series, for which N has respectively the 

 value io'5, 13, 27, &c, but always with the same result, so that 

 he concludes that these equivalences are not chance coincidences, 

 but that it is really possible to replace a certain number of atoms 

 of one kind by a certain number of another kind without pro- 

 ducing in the value of N an alteration which conies within the 

 limits of precise observation. 



