No. 7.] WHITTLESEY— LE\ELS OF LAKES. iOO 



Ahaz Merchant, I. N. Pillsbury, late City Engiueer, Captain 

 B. Stanard and myself, extending from 1834 to 1859, but not at 

 regular hours, nor on consecutive days. The labor is too great 

 for any person to undertake who is not employed for that purpose. 

 In addition to the observations made at Detroit, by the first 

 Geological Survey and by A. E. Hathan, City Engineer, and 

 Jacob Houi>hton as Enirineer of the Water Works, there have 

 been a large number of readings at Black Rock, and at Buffalo, 

 New York, by the Engineers of the Erie Canal. All these can ' 

 be brought together and thus made to supplement each other. 

 On the supposition that the Lake in calm weather is approxi- 

 mately levels readings made here and at either of the other j^laces 

 at the same time, may be regarded as representing one plane sur- 

 face. The Detroit gauge is higher than the others by the des- 

 cent of the river from there to Lake Erie; but the fluctuations 

 are in cousouanee with those in the Lake, and therefore may be 

 used. After the water tables at Detroit, Cleveland and Buffalo 

 were made out, it appeared that they had some periods of time 

 in common, and thus they could be brought together as one 

 series of observations, aood for the entire Lake. 



For instance, ]Mr. John Lothrop, an intelligent engineer in 

 the employ of the State of New York, and myself, made obser- 

 vations for the month of July 1851. The average for that mouth 

 at Cleveland was 1.96 feet, and at Buffalo 9.46 feet above the 

 metro sill of the guard lock. 



This gives for the Cleveland zero 11.42 feet above the Buffalo 

 zero. At Detroit Mr. Hathan used the base of the tower of 

 Waterworks, and measured downwards from that as zero. By 

 comparing his tables with ours and disregarding the descent of 

 the river, I find his zero to be 3.43 feet above ours, or 14.85 

 above bottom of Canal at Buffalo. 



Li this manner, I have combined all the reliable monthly 

 averages from 1838 to 1853, at the three ports of Buffalo, Cle- 

 veland and Detroit, into one expression in the form of curves, as 

 shown in the engraving on the next page. 



