74 ESSAY ON IRRIGATION. 



The experiments of Mr. Cavendish and Dr. Priestley liave 

 sufficiently proved that vegetables have the power of decompo- 

 sing water and converting it into such fluids as they need for 

 circulation in their own vessels ; and that they elaborate from 

 this substance, such juices and fruits as they are by nature cal- 

 culated to produce. 



The great eftect which is so frequently observed to follow the 

 formation of ditches from the road-sides on to mowing ground, is 

 no doubt in part to be attributed to the manure which is thereby 

 washed on to the ground, but is also in part owing to the more 

 copious supply of water which it thereby receives. 



That pure water is capable of producing similar effects I have 

 the following experiments to prove. 



Several years ago when resident with my father on his farm 

 at Rowley, I labored hard to divert a stream, which fell into a 

 miry swamp, from its usual course across a piece of dry upland. 

 The stream was pure spring water, which issued between the 

 hills about fifty rods above, running but just far enough to acquire 

 the temperature of the atmosphere, but without receiving any 

 more fertilizing quality than was obtained in passing through a 

 pasture, in a rocky channel ; the effect, however, was to double 

 the quantity of grass. The same stream 1 again diverted from 

 its course about forty rods below, after it had filtered through a 

 piece of swamp or meadow ground, and with the same effect : 

 and again still lower down its course, I succeeded in turning it 

 on to a piece of high peat meadow which had usually produced 

 but very little of any thing, and the eftect was that more than 

 double of the quantity of grass was produced, and that of a much 

 better quality. I was led to this latter experiment by observing 

 that a strip of meadow which naturally received the water of this 

 run, and over which it spread for several rods in width without 

 any particular channel, was annually much more productive than 

 any other part of the meadow. 



But the best experiment, and on the largest scale of any which 

 I have known, was made by my late father-in-law, Dea. Eleazer 

 Spofford, then resident at Jaffrey, N. H. . A letter from Rev. 

 Luke A. Spofford, in answer to my inquiry on this subject. 



