reviews 355 



association with sub-lacustrine springs, while the mouths of streams and 

 the currents leading away from them are marked by deposits of muck 

 and silt. Calcium carbonate (CaC0 3 ) will be deposited if by any 

 means C0 2 be withdrawn from the double carbonate. The authors 

 recognize three such means. 



i. Increase in temperature from mingling with the warmer lake 

 waters. 



2. Decrease in pressure as the spring water rises to the surface. 



3. Extraction by aquatic plants, such as stoneworts, etc. 



Since more than half the marl lakes do not have the stoneworts in 

 abundance, and since the marl in general does not show that large per- 

 centage of organic matter which is shown by marls deposited through 

 the agency of the stoneworts, the authors are inclined to minimize the 

 part of aquatic plants. 



As the spring water is colder than the lake water and denser owing 

 to the carbonate in solution, we can see no cause for the rise of the 

 spring water, except diffusion, in which the CO, released by ascending 

 waters would be just balanced by that taken into solution by the 

 descending currents. 



If the main dependence is to be put upon the first means for 

 removing the C0 2 , i. e., increase of temperature, it seems to us that 

 springs which emerge superficially in the neighborhood of the marl 

 lakes would have their waters warmed more rapidly than sub-lacustrine 

 springs, and should thus have copious deposits of marl. No reference 

 is made to such deposits. We believe a competent theory for the 

 deposition of the marls is yet to be found. 



The state is to be congratulated on the timely appearance of this 

 report and will reap the benefits which accrue from early occupation of 

 the field. 



"The paper on the 'Silver Creek Hydraulic Limestone,' by Mr. C. 

 E. Siebenthal, contains full details regarding the location and stratig- 

 raphy of the stone so largely used in southern Indiana for the manu- 

 facture of natural rock cement, as well as an historic, descriptive, and 

 statistical account of the industry. It is accompanied by a map show- 

 ing the exact location of the cement rock."- 



Of the Bedford limestone 1 there was quarried in 1900 some 7,035,000 

 cubic feet, with a value of $1,699,649. 



1 The article on this subject contributed to the current report by the writer, was 

 made to read " Indiana Oolitic Limestone," without the consent or knowledge of the 

 author. 



