34 



percentage of volatile matter, and others with a large amount of 

 volatile matter burning brilliantly, but producing very little gas. 

 The distinction between gas coal and bituminous coal, can be 

 learned by more complete processes only, and his own experience 

 on this coal, soon after it attracted public notice, and with strong 

 hopes that it would prove a gas coal, did not lead to such a con- 

 clusion. 



Dr. D. F. Weinland called the attention of the Society 

 to a question now discussed in the European journals of 

 Ornithology, viz : The cause of the change of color in 

 the feathers of birds, and in the hairs of Mammalia, and 

 the manner in which this change is effected. 



It is a well known fact that many birds, particularly the 

 males, have a very differently colored plumage in ditferent sea- 

 sons ; for instance, that the male of many singing birds has a far 

 more beautiful plumage in the reproductive season than during 

 the rest of the year ; furthermoi'e, that many northern birds and 

 mammalia become pure white in winter, while they are yellow, 

 red, brown, gray, or of a still darker color in summer. 



Till within the last few years, this change of color was sup- 

 posed to be effected simply by the production of a new feather 

 or hair ; but there are on record several instances which are 

 entirely at variance with this supposition ; and Dr. Weinland was 

 of the opinion, that, although this change is generally produced 

 by molting, many instances are proved, by past and recent obser- 

 vations, in which it has taken place without loss of the feather. 



Human Pathology has shown many cases, in which the hair 

 of men, from sudden terror or from grief, has turned gray or white 

 in so short a time (sometimes in one night) that there was no 

 possibility of a change of the hair itself. A case is known in 

 Ornithology, in which a starling in one day became white all 

 over, after being rescued from the claws of a cat. 



These facts, however, seemed to be exceptions only, till quite 

 recently some distinguished Ornithologists — Schlegel in Leyden, 

 and Martin in Berlin — at the same time affirmed that many birds 

 get their wedding plumage without molting. 



Experiments were made by many Ornithologists; some affirmed 



