April 1891.] 



AND OOLOGIST. 



51 



Previously, however, on l\[ay 27th, I had 

 taken the nest of the species. On the day in 

 question, wliich hy the way was rainy and dis- 

 agreeable, I was accompanied by Mr. James 

 Myers, one of the local hunters and woodsmen, 

 who proposed that we should go to a nest 

 which he had found a few days before. After 

 a walk of about a mile, interrupted, however, 

 by an exciting adventure with a Blue Yellow- 

 backed Warbler, we came to a high woods 

 with a thick undergrowth of laurel and 

 huckleberry, where the bird was presently 

 flushed from her nest on the ground. I gave 

 one glance at the nest, another at the bird, 

 exclaimed " Wilson's Thrush!" and in a twink- 

 ling fired and killed her. Returning to the 

 nest, I found it to contain three eggs, of 

 exactly the same shade of bluish-green as 

 those of the Wood Thrush. They were, of 

 course, smaller, and, upon blowing, proved to 

 be .slightly incubated. The nest was not 

 sunken in the ground, but placed on a mound 

 of leaves, thus escaping the damp: it was 

 surrounded and canopied over with huckle- 

 berry bushes. Leaves, strips of bark and 

 weed stalks entered into its composition, with 

 broken leaves as lining. Measurements showed 

 it to be five inches in external diameter by 

 four and a half inches in external depth, with 

 a cavity two and three-quarter inches by two 

 and three-quarter inches. 



1 may add as a significant fact that I have 

 never as yet found this species in Beaver 

 County, either as a summer resident or as a 

 migrant, although the other species of the 

 genus native to the Eastern LTnited States are 

 abundant in their season. 



ir. E. Ch/ih- Tmhl. 



liejiver. Beaver Co., Pa. 



Ornithology and Geology. 



The intimate relati(ui existing between tlie 

 various sciences of to-day is too often over- 

 looked by many people. Each is for the gain 

 of knowledge after its own kind, but to insure 

 against the evil of self-worship, they are so 

 constituted as to necessitate a con.scious un- 

 derstanding of each of its brother sciences 

 before one can fully appreciate the bearings of 

 seemingly outside influences upon things of 

 its own sphere. 



I do not mean by this that an ornithologist, 

 amateur or otherwise, must neces.sarily follow 

 step by step into the abstruse dogmas of the 

 cosniologist or biologist, but neither is it 



profitable to ignore contemporaneous literature 

 of writers in other fields. He should adopt a 

 middle course and aim to obtain a general 

 knowledge of all, more or less extended, ac- 

 cording to its degree of intimacy with the one 

 he makes a specialty. It is, in fact, only a 

 division of labor, and the truism that the 

 division of labor is the gain of many is appli- 

 cable in this ease, and if the specialist does not 

 adopt this course he has no division, but in 

 its place are many small units, disconnected 

 with each other. 



As an object lesson to illusti-ate this state- 

 ment the writer has purposed a series of 

 papers especially designed to show the rela- 

 tion of several of the more important contem- 

 poraneous sciences to that of ornithology, the 

 first of which I have designated by the above 

 title. The science of geology is so many- 

 sided that it is at first diflicult to separate those 

 branches which are the more probable to have 

 an intimate connection with bird work, and it 

 must not be expected that this paper will give 

 more than a few briefly treated examples. 



A knowledge of surface geology is an im- 

 portant factor in the study of distribution and 

 the confining of various genera and species to 

 five areas, and are therefore briefly alluded to: 

 The several continental area divisions, -separ- 

 ated as they are by vast expanses of water, 

 are prima facie markedly separated areas, but 

 there are also several other classes of restric- 

 tive barriers, as mountain chains, river sys- 

 tems, etc., the former being most often active 

 agents in separating faunas of contiguous 

 areas, and the larger tracts of desert or 

 otherwise arid lands act in a similar mamur. 

 With rivers there are several cases, some of 

 which are cited by Darwin and by Wallace, 

 where birds common on one side of a stream 

 are wholly wanting on the opposite shore. 



To surface geology we also look for a solu- 

 tion of tlie phenomena of remotely distrib- 

 uted f(nms found in isolated areas, as the 

 workers in that field have conclusively shown 

 that in many cases land connection was 

 formerly present, but now sunken beneath the 

 level of the sea, while the alternation of warm 

 and cold climates during the glacial periods 

 played an important part in distribution, as 

 many species iuhabiting frigid or moderately 

 cool climates occupied a large and continuous 

 district during the presence of an ice cap in 

 New England, throughout the northern part 

 of the United States, but retreated northward 

 with the receding ice leaving a place to be 

 filled by other forms, except where such 



