536 Transactions of the American Institute. 



they lose the protecting influences which surroimcl them in the great 

 forests. Many farnaers, having left noble specimens, are mortified 

 that they foil before the high winds. Nor are they so long-lived 

 as has been supposed. It would seem, then, that the trees to be 

 left should be of the smaller kind, and so thinned out that they 

 can attain a spreading and stocky growth. In other parts of the 

 country, where by reason of the soil the trees send down long top 

 roots, and when their grain is tougher, the rule may vary. Still, 

 as a general thing, it must be said that to keep up a supply of 

 forest trees, we must resort to planting and preserving trees on 

 rocky and hilly lands. 



THE CHE>nCAL ACTION OF CERTAIN FERTILIZEES. 



Prof Horsford, of Cambridge, Mass. — The extraordinaiy crops 

 that have been produced during the last few years by the use of 

 tfuperphosphate of lime on the Seekonk Commons, which, for many 

 years previous, had scarcely produced moss, natiu-ally led to the 

 Inquiry, "Where do these crops get their potassa?" The porosity 

 t<f the soil, which permits the heaviest rains to be rapidly swal- 

 lowed up and leached away, only embarrassed the inquiry. Solu- 

 ble potassa, naturally present in the soil, could not long remain 

 within the reach of the roots of plants, and yet, as the fertilizer 

 does not contain potassa, and as by its use astonishing crops have 

 been produced which require potassa, the ingredients could not 

 cmly come from the soil ; moreover, it must have been present in 

 the soil in insoluble form until the fertilizer was introduced. Now, 

 for the most part, the soil is drift sand, derived from the disinte- 

 grated rocks of New England. These are known to be mainly 

 gneiss and sienite, composed of quartz, feldspar, mica and horn- 

 blende, with smaller proportions of other minerals and calcareous 

 varieties. From these the crops must derive whatever nourish- 

 ment is not drawn from the air or supplied by manures. From 

 these, which, in a state of greater or less subdivision, exist in the 

 soil of Seekonk Commons, enriched only by acid phosphate of 

 lime, sulphate of lime, and sulphate of ammonia, crops must derive 

 their potassa, and to -some extent their magnesia. But how are 

 they obtained ? This was ascertained by practical experiment. 

 Feldspar, which is a compound of silica, potassa and alumina, was 

 pulverized and treated with acid phosphate of lime. The free 

 pl^osphoric acid of the superphosphate of lime seized the potassa 

 Gi the feldspar, disengaged it from the silica and alumina, and 



