92 PROCEEDINGS OF THE AMERICAN ACADEMY 



even the fossil skeleton would not teach. Hence the importance of 

 large collections of the footmarks. Professor Hitchcock stated that 

 he had counted the individual tracks in the Amherst Cabinet, and 

 found them to exceed 12,000, nearly 4,000 of w^hich are the tracks of 

 insects. Within a few days, through the liberal donations of a few 

 friends of science, the entire collection of Roswell Field, made at 

 Turner's Falls, has been added, which will increase the collection by 

 several thousand tracks. May they furnish new light to future ex- 

 plorers ! 



[Postscript, January 15, 1863. Among the specimens just added 

 to the cabinet, as mentioned above, are some very perfect ones, show- 

 ing the phalangeal impressions with great distinctness. And one of 

 them, probably a new species of Anomoepus, has in the outer toe, be- 

 sides the hindmost impression, which I now regard as made by a heel- 

 bone, four other perfectly distinct impressions in at least two tracks. 

 Here, then, we have the normal number for birds, after setting aside 

 the hindmost. Again, on another quite perfect sjjecimen of a Grallator, 

 I find the same facts, — not so distinctly marked, indeed, as in the first 

 case, still obvious enough to a practised eye ; and now that attention 

 has been directed to this point, I am anxious to re-examine all my 

 specimens of the fourteen thick-toed bipeds, to see whether they may 

 not all have had the same number of protuberances. I incline to the 

 opinion that it may so turn out ; and if so, that we may still confidently 

 maintain that these species were birds. — March 20. It so turns out.] 



Dr. B. A. Gould directed th.e attention of the Academy to 

 an echo, of remarkable excellence, in the chimney of the Rox- 

 bury Chemical Works. 



The buildings have been recently taken down, with the exception of 

 this tall chimney, which must be nearly two hundred feet high, and 

 into which entrance is easy by means of large, door-like flues. Sounds 

 made within the structure are repeated with great distinctness many 

 times, — and repeated trials showed the possibility of obtaining at 

 least ten clearly audible repetitions, for sounds of moderate strength 

 and low pitch, such as that made by stamping with the foot upon the • 

 frozen ground. The nearest estimate which Mr. Gould could make 

 with the aid of a common watch, gave 3^4 or 3^5 as the interval 

 between the primitive sound and the tenth echo, — corresponding to 

 a series of reflections from the open end of a pipe about one hundred 

 and ninety feet high, at the temperature of freezing. 



