314 ANNUAL OF SCIENTIFIC DISCOVERY. 



modern, are of high antiquity in relation to the human inhabitants of 

 New Zealand, and considers it probable that these stupendous birds 

 formerly ranged over a vast continent, now submerged, and of which 

 the islands of the Pacific are the culminating points. Although there 

 seems to be but little doubt that, like the Dodo and Solitaire of the 

 Mauritius, and the gigantic elk of Ireland, the last of the Moas was 

 exterminated by human agency, yet it is probable that a change in 

 physical conditions had prepared for their final annihilation. Of the or- 

 ganic law which determines the extinction of a race of highly organ- 

 ized beings, and whose effects through innumerable ages paleontology 

 has in part discovered, we are as utterly ignorant as of that which gov- 

 erns the first appearance of the minutest living organisms the powers 

 of the microscope enable us to descry ; both are veiled in inscrutable 

 mystery ; the results only are within the scope of our finite compre- 

 hension. Silliman's Journal, May. 



RECENT IMPRESSIONS OF THE FEET OF BIRDS. 



MR. J. L. HAYES stated that Dr. Webster, of Nova Scotia, had 

 lately procured some specimens of recent bird-tracks in the sand of the 

 Bay of Fundy, which were precisely like the fossil bird-tracks of the 

 sandstone of the Connecticut valley. The enormous tides of this Bay 

 wear away the sandstone, and deposit it on the neighbouring beaches 

 to the depth of from half an inch to an inch at each tide. Dr. Web- 

 ster carefully removed some of this sand bearing the footprints of 

 marsh birds, and baked it so as to preserve the impressions perfectly. 

 It was even found that, in splitting these slabs into layers, the impres- 

 sions of the track could be traced through three or four of them, as in 

 the fossil specimens. The same success attended his experiments on 

 the impressions of recent rain-drops. Dr. Gould mentioned that he 

 had seen similar specimens from Nova Scotia baked by the heat of the 

 summer sun, during the recess of the tide ; and Mr. Lyell also obtained 

 specimens, which were so satisfactory as to convince English geolo- 

 gists that the fossil bird-tracks w r ere really what they had been consid- 

 ered by American geologists. Proc. Boston Society of Natural His- 

 tory, Feb. 



ON THE REPTILIAN FOOTPRINTS IN THE CARBONIFEROUS ROCKS 



OF EASTERN PENNSYLVANIA. 



DURING the year 1849, Mr. Isaac Lea, of Philadelphia, announced 

 the discovery of reptilian footprints in rocks which he considered to 

 belong to the old red sandstone, underlying the carboniferous forma- 

 tion of Eastern Pennsylvania.* The strata in which these tracks oc- 

 cur have since been carefully investigated by Prof. H. D. Rogers, who 

 has ascertained that they belong truly to the carboniferous red shale, 

 and are, therefore, of an age essentially later than that attributed to 

 them. In a communication made to the American Association, Prof. 



* See Annual of Scientific Discovery, 1850, p. 2?1. 



