117 



in sugar. This is no doubt due to a too liberal supply of nitrogenous 

 manure, and the non-application of lime and magnesia. Let cane-growers 

 note that a good soil for their purpose should contain at least 0.97 per 

 cent, of lime and 0.3 per cent, of magnesia." 



It is important to notice that if the magnesia occurs in the soil 

 in the form of silicate of magnesia, it is not available for plant food, 

 and the compound is rather an index of the want of fertility of the soil. 

 This is pointed out in the following letter by Dr. Phipson, which ap- 

 peared in the Sugar Cane for last February : — " For a long time past I 

 have made analyses of the West Indian cane soils, with the view of as- 

 certaining their respective values for cane growing, and the treatment 

 they should undergo in certain special cases. It results from the exami- 

 nations that the clay in which the sugar cane grows is so fertile natu- 

 rally that were proper tillage always available, nothing more would be 

 necessary to ensure ample crops of healthy cane. It is, perhaps, not too 

 much to assert that a couple of centuries of cme growing will not ex- 

 haust many of these soils. 



" I find exactly the same nature of clay in Barbadoes, J amaica, and 

 British Guiana, showing how intimately, in this respect, the islands are 

 connected with the main land, in spite of the distance. Those clays in 

 which the amount of lime soluble in acids is higher than that of the 

 magnesia are usually the most productive of sugar, and, generally speak- 

 ing, have been worked for a shorter period of time. 1 he magnesian 

 element, in the shape of a partially weathered silicate of magnesia, is 

 the chief enemy to fertility in these soils ; when it happens to abound 

 the soils give decidedly poorer crops, end this is a fact well worth know- 

 ing to those who are about to purchase canefields, or are thinking of 

 taking in new land. I have also found in many of these clays a slight 

 amount of vanadic acid, a substance which was first made known by me in 

 many English and foreign clays ( Journal of the Chemical Society, 1863 ) 

 Wherever vanadic acid is found in clays there is generally much phos- 

 phoric acid also." 



Ulbricht last year again points out the value of a mixture of mag- 

 nesia with lime, but adds a ( aution against magnesium carbonate. Ac- 

 cording to him, burnt lime poor in magnesia, heavily applied (710 lbs. per 

 acre), decidedly delayed the ripening of oats, while a similar application 

 of gray lime produced much less marked results, This difference is as-^ 

 cribed to the high percentage of magnesia in connection with lime in 

 the gray lime. Caustic magnesia (burnt magnesia), as well as magnesia 

 carbonate, had a highly injurious effect on oat plants, proving actually 

 poisonous in large amounts. 



This injurious effect was not always prevented by simultaneous appli- 

 cations of caustic lime or calcium carbonate. Barley was more resistant 

 to the injurious action of the magnesia than oats, 



COFFEE SEPARATING MACHINES. 



In the article on Liberian Coffee in Bulletin for January, 1894, a 

 mistake was inadvertently made on page 5 in the insertion of the wrong 

 illustration of separator. 



