Diary of a JVaturalisL , 21 



with a view to compute the period of its age.* If I have not mis- 

 conceived the operation of this river, it will now be seen that 

 the elements of this problem are too complicated and vague, to 

 offer any hopes of a satisfactory solution. Under the view I have 

 taken of it, its future retrocession will be very slow. Time, how- 

 ever, will last longer than the carboniferous limestone can 

 probably resist such influences as it has already yielded to. 

 When the cataract shall reach lake Erie, geology will possess 

 one great monument of the power of water to excavate gorges 

 of great length and height. 



THE DIARY OF A NATURALIST. 



Or Memoranda of the weather ; arrival of birds ; flowering of plants, &c. for the 

 spring of the year 1830. Kept at the " Bartram Botanic Garden," on the right 

 bank of the river Schuylkill, below the city of Philadelphia. By John B. Carr. 



TO THE EDITOR OF THE MONTHLY AMERICAN JOURNAL. 



Dear Sir — I send you for publication " The Diary of a 

 Naturalist," kept at my particular request, during the spring of 

 1830. If the observations are not so complete as the interest of 

 the subject might imply, it must be recollected that the author 

 seldom extended them beyond the immediate sphere of his daily 

 occupations. — Having the most perfect reliance on the ability 

 and talents of Mr. Carr for pursuits of this nature, I have pe- 

 rused the " Diary" with much satisfaction, and cannot doubt 

 that the subject which it embraces will be viewed with similar 

 interest by yourself and readers. — I have the honour to be most 

 respectfully, &c. R. IJarlan. 



March 1. Wind, a strong north-east, with snow and rain. 

 Large flights of robins, (turdus migratorius,) feeding on the red- 



* Mr. Lyell, in his principles of Geology, (Vol. I. p. 181,) has, — supposing that 

 the disintegrating power of the volume of the Niagara river, will at all times be 

 equal, at every point of its course — ventured on a computation, that, at the rate 

 of fifty yards in forty years, lake Erie will be reached in the course of thirty 

 thousand years. That the recession of these falls is effected as Mr. Lyell supposes, 

 we have never doubted ; but a long and familiar acquaintance with the cataract, 

 has induced us to adopt the opinion we have just seen announced by the Rev. 

 W. D. Conybeare, (Annals of Philosophy, No. 52. April, 1831. Page 267,) that 

 in forming the first estimates of this computation " some partial degradation of the 

 strata has here been mistaken for the general retrogradation." 



