WITH THE SILICATES. 169 



4. Do they, in any material degree, alter the strength, ap- 

 pearance, or quality of the straw of the corn-crops? This 

 question may be answered by the same series of experiments 

 which is required for the solution of the first and third questions. 



5. Do they act as silicates, or only in virtue of the potash 

 and soda they contain? This suggests comparative experi- 

 ments with these silicates, and with the equivalent quantities of 

 the carbonates of potash and soda, which will act in the soil and 

 upon the plant in the same way as the alkaline matter of the 

 silicates after they have been decomposed in the soil. They 

 may also be tried against equivalent quantities of chloride of 

 potassium and of common salt the latter of which, as I have 

 already stated, has been found to have a beneficial influence 

 upon the appearance and strength of wheaten straw. 



6. Lastly, it is worthy of inquiry whether the composition 

 of the soil, the nature of the burned lime applied to it, or the 

 composition of the springs or streams that water it, have any 

 influence in modifying the action of these silicates. This 

 inquiry is less purely practical than the others, and demands 

 more chemical skill ; but it is deserving of the careful attention 

 of those who possess at once the practical facilities and the che- 

 mical skill it requires. 



