MEMORIAL OT? CHARLES A. DAVIS 21 



building plant is the alga — a form related to Oscillaria, I think, which makes 

 the nodules or concretions such as you found at Hamburg Junction. Here the 

 more exposed and wave-washed shores are full of them; there are no other 

 stones or pebbles on the entire lake. Shells of the usual lacustrine forms are 

 fairly abundant, but of the more fragile types, and while they undoubtedly 

 help form the deposit they are not the controlling factor or a very important 

 one. I have undertaken to direct a survey of the lake and the marl and so 

 shall go up again, and 1 hope you will go with me sometime. Steele has a set 

 of instruments and is the man I am going to try for taking levels and plotting, 

 if I can get him. I might add that the marl for some feet on top is of a dis- 

 tinctly granular type, but below is fine grained. I think that deposited in 

 deeper water is the finer matter washed from the shores; that on top the 

 coarser, sorted by wave and current action. I believe I can use this matter in 

 my paper on vegetable origin of the marl to advantage." 



"Alma, Michigan, August 29, 1900. 

 "Got home last night and found, among other papers that had accumulated 

 since my departure, a short paper which I got track of in Ann Arbor on 'Cal- 

 careous pebbles formed by algae,' George Murray, London, 1895. It describes 

 and figures the marl pebbles exactly and of course must be embodied in my 

 paper, especially as the material came from a 'pond in Michigan.' " 



"Alma, Michigan, September 1, 1900. 

 "I find the amount of Chara in Cedar Lake is simply immense. I counted 

 from 50 to 80 tips of growing plants to the square centimeter — that is, the 

 plants were simply so closely crowded that there was no chance for anything 

 else to grow, and if my results of solid matter per plant are anywhere near 

 average ones, as they certainly are, the amount of solid matter precipitated to 

 the square centimeter of bottom is very considerable. The Schizothrix is also 

 apparently abundant, but is not, so far as I could find, making pebbles at 

 present at Cedar Lake, although the pebbles are common in the marl." 



The way Professor Davis discovered calcium succinate in marl is shown 

 in the following letters : 



"Alma, Michigan, Decemher 1, 1900. 



"In looking over some marl analyses in which the CO, was determined sepa- 

 rately, I notice that the CO, is deficient, if we assume that the Ca and Mg are 

 all combined with CO3 or with the other inorganic acid radicals present in the 

 same analyses. It is probable, then, that some of the 'organic matter' is com- 

 bined with the Ca in some way, as, for instance, as oxalate or tartrate or some 

 other organic acid radical which does not yield CO. with dilute acids. 



"I wish, if you have time, you would look over the marl analyses you have 

 and see if the CO, would hold out for the Ca and Mg as carbonates— in those 

 cases in which the CaO and MgO and CO, have been determined separately. 

 If, in general, it is true that the CO2 is deficient, then we have another step in 

 the proof that the marl is a Chara, etcetera, product, especially if it can be 

 demonstrated that the same compounds exist in the marl and in the plant." 



