COMPOSITION OF THE SILICATES. . 165 



be used with much advantage. It is not impossible that they 

 may even be found capable of profitable use by the practical 

 farmer. I would, therefore, suggest that accurate comparative 

 duplicate experiments should be made. 



1. With each of the phosphates of potash and soda upon 

 different crops, and applied in different equivalent proportions. 



2. With the two phosphates tried against each other upon 

 the same crop, under the same circumstances and in equivalent 

 quantities. 



3. With each phosphate applied at different seasons, or at 

 different periods of the plant's growth. 



4. With each phosphate in equivalent quantities divided into 

 two or more portions, to be applied at successive periods. 



5. With each phosphate applied to soils of different qualities 

 and composition. I would especially suggest such comparative 

 trials on soils which abound in, and which are poor in lime 

 respectively. 



The results of these experiments will indicate what ought 

 next to be done in the way of practical trials with these 

 substances. 



7. Composition of the silicates of potash and soda, their 

 properties and their functions in the soil and in the plant. 



1. Composition of the silicates of potash and soda. 



a Silicate of potash, prepared by melting one part by weight 

 of carbonate of potash with three of silica, (pounded quartz, flint 

 or silicious sand,) consists of about silica 82, and potash 18. 

 Prepared by melting one of carbonate of potash with two of 

 silica, it consists of about 75 of silica, and 25 of potash. 



b Silicate of soda, prepared by melting together one part by 

 weight of dry carbonate of soda with three of silica, consists of 

 about 84 of silica, and 16 of soda. By fusing together one of 

 dry carbonate of soda with two of silica, it consists of about 58 

 of silica and 22 of soda. 



Both of these silicates, however, arc liable to considerable 

 variations in their composition as they are usually prepared 

 with the view of being sold for agricultural purposes. They 

 contain for the most part a larger proportion of soda or potash 



