MEMORIAL OF CHARLES A. DAVIS 23 



"(6) If the spring water rose to the surface, there would be a certain re- 

 lease of pressure, which would also permit release of CO2, and, if the satura- 

 tion point were reached, some precipitation. Again, we have to consider how 

 great this pressure is, probably. Moraines 100 feet high above the level of 

 lakes in their vicinity are rare in Michigan, so far as my observation goes. 

 The ground water level does not often extend very high into even those which 

 are more than 100 feet high. At Cedar Lake, I think, they said the flowing 

 wells there had a head of about 20 feet, which is unusual for this region. 

 Here at Alma the head of the wells with lowest outlets is about 20 feet ; others 

 with strong flows about 10 feet, etcetera. Assuming, however, that a spring 

 has a head sufficiently high to make it break out in the bottom of a lake, it is 

 not likely that the pressure upon it is very great when we get only an atmos- 

 phere pressure for 33° -f feet of H2O." 



"Alma, Michigan, August 15, 1901. 

 "I have been meditating on the spring idea, and I think the fact that in tea- 

 kettle scale, which is precipitated by release of CO2 and raising the tempera- 

 ture, we always have the Fe thrown down and showing its presence by yellow 

 stain is perhaps the best line of argument to show that marl is not due to 

 these causes. In the same line of demonstration may be mentioned the fact 

 that the precipitate that forms in the water from the flowing wells which come 

 from glacial clays in this region, and which in some waters' forms freely as the 

 water stands and gets warmed up at the ordinary one-atmosphere pressure, is 

 always well colored with Fe ; in fact, give a distinct fulvous or even red stain 

 to glassware and other forms of holders that are exposed to it. This precipi- 

 tate is a mixture of Fe and CaOOs', mainly the latter. But the Fe is always 

 abundant enough to give a distinct color, while in marl it is only where springs 

 run over the surface of the deposits and their mineral contents are manifestly 

 precipitated by exposure to the air that we get any traces of yellow; and here, 

 as you and I have both noted, the staining is local and evidently due to the 

 effects of the spring itself. In other words, the marl is the result of selective 

 chemical action and not of such general causes as relation of temperature and 

 release of pressure, even if the degree of saturation of the spring waters is 

 sufficient to allow these causes to become operative in our marl lakes, which is 

 very doubtful, and the doubt even capable of demonstration from existing 

 data, perhaps." 



At Ann Aubok 



At about this time the "inexhaustible supplies of pine" of the Saginaw 

 Valley were exhausted and the Saginaw salt "blocks" — that is^ factories- 

 shut down for lack of their fuel of sawmill waste, and the American people 

 ])egan to awake to tlie fact that they must, like the European nations, 

 grow their own timber. Prof. Yolney M. Spalding, of the department of 

 botany of Ann Arbor, recognizing that Davis was, what Newcombe called 

 him, the best field l)otanist of the State, invited him to organize the for- 

 estry courses at Ann Arl)or. This he proceeded to do after a half year in 

 the forestry school at Cornell in 1900. 



