26 RELATION OF LIME AND MAGNESIA TO PLANT GROWTH. 
these sediments is by no means large, that of the former varying from 
0.10 per cent (Colorado) to 0.28 per cent (Rio Grande), that of the 
latter from 0.092 per cent (Rio Grande) to 0.27 per cent (Colorado, 
near Fort Yuma, Ariz.). The amount of lime and magnesia in some 
of these sediments was found as follows: 
Amount of lime and magnesia in some river sediments. 
Per cent | 
= od Per cent = 
Rivers. aie iene ot erat 
IN tl (eyed Doan 0 elle ee ene ee ERG Se On SA aie ls sa ONS ee 1.725 0. 046 
Rio Grande NeweMexiGO!2s =. a. ee Aaee eee eee me cere mere. 4. 384 0.080 | 
Colorado River, Nevada, near Cottonwood Island?2.............--- 7.000 0.690 | 
1Knop (1873) mentions, in his analyses from two different localities on the Nile, calcium carbonate, 
3.30 and 4 per cent, and magnesium carbonate, 0.78 and 0.28 per cent. The analysis in the table 
relates to another locality. 
2Annual report of the U. S. Geographical Surveys west of the 100th Meridian, Capt. George M. 
Wheeler in charge, Washington, 1875. The sediment of the Colorado River from the vicinity of Fort 
Yuma, Ariz., was analyzed in the Agr. Exp. Sta. of Arizona, Bul. No. 6. 
Sediments in western Switzerland claimed to be very fertile, depos- 
ited by the Morges, the Sionne, and the Borgne, show lime, 2.34, 21.70, 
and 22.82 per cent; magnesia, 1.16, 1.25, and 1.12 per cent. 
It will be seen from the above review— 
(1) That the ratio of lime to magnesia ranges between wide limits. 
(2) That in the majority of cases lime predominates over magnesia. 
(3) That in all the instances of great fertility the soil never shows 
any marked excess of magnesia over lime, but, on the contrary, 
generally more lime than magnesia. 
In many of the above-cited instances, however, safe agricultural 
conclusions can not be drawn, since the mode of analysis (treatment 
with hydrochloric acid) does not admit of distinguishing between 
easily and difficultly available mineral nutrients. 
SOME SPECIAL PHYSIOLOGICAL CASES RELATING TO THE RATIO 
BETWEEN LIME AND MAGNESIA. 
Some physiological instances may now be considered which relate 
to the ratio between lime and magnesia. 
Knop’ infers from his investigations with barley that two molecules 
of calcium nitrate should be present in the culture solution for one 
molecule of magnesium sulphate, which would correspond nearly to 
the proportion of 1 part of lime to 0.5 of magnesia. E. Wolff caleu- 
lates, however, for the minima of lime and magnesia required for the 
production of the dry matter of the oat plant 0.25 per cent lime and 
0.20 per cent magnesia, or a ratio 1:0.8. 
1Centralbl. f. Agriculturchemie, 1861, pp. 465, 564, and 945. 
