-VO. VIIL] EXPERIMENTS UPON GRASS AND MIXED CROPS. 73 



nitrate and sulphate, another illustration of the kind of struggle we may suppose 

 to go on between substances tending respectively, the one to increase, the other 

 to diminish, the produce. In the joint action of the common salt and the soot, 

 when applied together, we have a further instance of the same kind — an increase 

 of 4 cwt. only being caused by the application of 16 bushels of soot, when coun- 

 teracted by an admixture of 2 cwt. of common salt. Applied alone, the increase 

 of produce would probably have been greater. Will any one undertake exper- 

 iments with the view of further bringing out this interesting mutually-counter- 

 acting influence of different applications'? 



6°. I can only call attention to tlie large yield of hay naturally obtained from 

 that part of the field on which barley dressed with bone-dust in 1841 had previ- 

 ously grown : Mr. Fleming informs me that no sensible difference in the produce 

 of hay was ooserved between the undressed part of the field and that upon which 

 the dressed wheat had grown in 1841, though the crop was not set apart or 

 v/eighed, as we might wish it to have been. 



III. Since the preceding experiments went to press I have received the fol- 

 lowing short notice of trrals upon hay made by Mr. Campbell, of Islay : — 



" It is very difficult to get the tenants in our wild part of the world to expend 

 money in the purchase of foreign substances, however beneficial ; and for this 

 reason I have been induced to try the substances mentioned below, because, 

 with the exception of sulphuric acid, the others are to be got in abundance 

 in the island — the pigeons' dung may be got in large quantities in the caves, 

 sea-ware on the shore, and lime is abundant and excellent in quality. The ex- 

 periment was made thus — 



WEIGHT IN POUNDS. 



Fresh cut. Dry. 



1. Nothing 240 199 



2. Pigeon Dung 318 275 



3. Sea-ware, Lime, and Sulphuric Acid . . . SOG 269 



4. Lime and Sulphuric Acid . . ^ . . . . 293 256 



1. A field of about ten acres, lately improved from heather, was chosen; the 

 field was well drained and deep ploughed, so as to raise the subsoil (red loam) 

 with the moss. On its surface the grass was sown down with oats--8 cwt. of 

 each substance was used to the acre. Eight yards square carefully measured 

 from the centre of each variety, and weighed the day they were cut, and again 

 on the day they were put into stack. 1 he hay was fully ripe when cut. 



2. The pigeon dung, which looks like peat-dust, was laid on exactly as it 

 was taken from the cave. 



3. One ton of lime-shells was mixed with 12 tons fresh sea-ware; after being 

 twice turned, the whole of the sea-ware was consumed, leaving only small black 

 particles mixed with the lime : the bulk was reduced to five large carts (not 

 weighed) ; 4 galls, sulphuric acid, mixed with 400 galls, of water, were added to 

 the powder — a violent fermentation took place, and the bulk was further re- 

 duced about an eighth. 



4. A ton of lime-shells was prepared according to your recommendation 

 slaking the lime with the dilute acid. 



N. B. One measure of this lime in shells gives three and a half in powder." 



G. — The Experiments upon Mixed Crops. 

 Mr. Alexander's experiment upon a field of mixed oats, beans, and peas, is 

 very deserving of notice, and will, I have no doubt, be repeated. Not only did 

 the mixture of gypsum and common salt increase the ultimate produce — but, as 

 Mr. Alexander- says, it acted like magic — imparting life and vigour to an appa- 

 rently dying and worthless crop. 



H. — The Experiments upon Beans. 

 I. The principal fact of importance in the experiments of Mr. Alexander is 

 the effect he found his mixture of gypsum and common salt to produce upon the 



