HYDROLOGY OF NEW YORK 



121 



ant in estimating the permanency of a stream. Aside from Mr 



Vermeule's, the most satisfactory discussion which the writer 



has seen is that of Mr W. S. Auchincloss. 1 This paper, while too 



long to be abstracted, is nevertheless very interesting, because the 



author recognizes the limitations of averages. On page 10 7 after 



giving a table of the average rise of his sublake, he states : 



Since the table was built up from averages, we must not expect 

 it to emphasize special variations, for the grouping of averages 

 resembles the grouping of pictures in composite photography. 

 The combination invariably brings out class likenesses to the 

 exclusion of individual features. Thus the table loses sight of an 

 extraordinary year like 1889 — full of plus quantities — also seasons 

 of drought, like 1894 and 1895. It, however, clearly shows that 

 influx has a tendency to prevail between February and July, in- 

 clusive, and efflux to hold the mastery during the remaining 

 months of the year. 



Though this paper does not fully recognize the wide variation 

 occurring in different localities, this is probably not due to over- 

 sight, but merely to the fact that the author was discussing a 

 specific case. The observations recorded were made at Bryn 

 Mawr, Pa. The paper is valuable and well worth the attention of 

 students of hydrology. 



Vermeule's formulas. These formulas are somewhat different 

 from those previously considered. Mr Yermeule claims to have 

 discovered a relation between evaporation and mean annual tem- 

 perature. For the relation between annual evaporation and 

 annual precipitation on Sudbury. Croton and Passaic rivers he 

 gives the following: 



E = 15.50 + 0.16 R, (18) 

 In which E = the annual evaporation and R = the annual 

 rainfall. 



In the original publication of this formula, in the Report of the 

 Geological Survey of New Jersey, 2 Mr Yermeule allowed for other 

 catchment areas an increase or decrease of 5 per cent from values 



lOn Waters within the Earth and Laws of Raiuflow, by W. S. Auchin- 

 closs, C. E. Philadelphia, 1897. 



2 Report on Water Supply, Water Power, the Flow of Streams, and 

 Attendant Phenomena, by C. C. Yermeule: Final Report State Geologist of 

 New Jersey, Vol. III. Trenton, 1894. 



