178 



This was the case in ali the little lakes in this region of country 

 and in Lake Ilopatcong also, which is pretty large and can hardly 

 he classed as a little lake, as I learned from conversation with inha- 

 bitants of the neibourhood of Blairstown who had been born in that 

 region of country and knew the lakes well. In fact one of them 

 was a civil engineer and had Iravcrsed the country far and near and 

 although not a geologist was a dose observer of the soil and the 

 lay of the land. So that 1 trust them for what was the general cha- 

 racter of the land in that region although I was only at and near 

 Blairstown nine days. 



I will now quote from the Annual Report of the State Geolo- 

 gist for New Jersey for 1890 the following from a Report on the 

 Portland Coment Industry by Henry B. Kummel, Ph. D. «In this 

 connection the shell-marl deposits of White Pond » (White Pond, 

 Marksboro is about four miles from Cedar Lake, Blairstown) « may 

 be mentioned. The shores and bottom of the pond are covered with 

 a thick deposit of shell mari which exceeds fourteen feet in thickness 

 at many places. A partial analysis of this mari is bere given ('). 



Analysis of Mari from White Pond. 



Carbonate of lime 92.25 (Lime. 5 1.66) 



Carbonate of Magnesia .... 2.98 (Magnesia. 1.42) 



Sand and day i.5ó 



Water, vegetable matter, etc. . 3.2 1 



100.00. 



Besides the mari I collected the magnesian limestone (called 

 the Trenton limestone by the geologist of New York) and the slate 

 which is common there. The magnesian limestone mari is of the 

 same chemical composition wherever it is found, containing from 

 43 to 5o percent of lime and 33 to 38 per cent of carbon dioxide, 

 commonly known as carbonic acid. Magnesia is present in less than 



(') Animai report of tlie State Geologist for 1877, p. 24. 



