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THE SOUTHERN PLANTER. 



RAIN- EVAPORATION AND FILTRATION 



We have before mentioned a paper, pre- 

 pared for the transactions of the New York 

 State Agricultural Society for 1854, on this 

 subject, by Hon. Geo.„Geddes. From an atten- 

 tive perusal of it, we find it contains matter 

 which would be very valuable to the farm- 

 er. Meteorogical facts have not received that 

 attention from the agriculturalist, and not un- 

 til recently from the government, that they 

 deserve. Mr. G-eddes well remarks, that 

 " One of the things to be looked at in select- 

 ing a new home is the rain-guage, and the gov- 

 ernment would do the world a great favor to 

 have rain-guages kept at all the frontier posts, 

 and at every station in the country, and pub- 

 lish the reports, property arranged in tables, 

 for every work." 



It has been ascertained from records kept 

 in various parts of Europe and America, that 

 there is annually more rain along the Atlantic 

 coast than in the interior. But the wants of 

 agriculture do not depend so much on the 

 quantity of water as on the manner in which 

 it falls. Thus, some districts which in the 

 course of the year receive an unusual quantity 

 of rain, suffer much from djouth. In Eng- 

 land the annual fall of water is stated to be 

 32 inches. Along the Atlantic coast of the 

 U. States it is at different points from 38 to 40 

 inches, and in the State of New York, taking 

 the average from about forty points of obser- 

 vation, it is 35 inches. Yet the climate of 

 Britain is much more moist than that of the 

 United States, There the number of rainy 

 days is greater, and the rains more moderate 

 than here. There is also a great variation in 

 different parts of our own country. In the 

 warmer and more level portions, rains often 

 come in heavy showers, washing and packing 

 the earth injuriously ; in the cooler and more 

 mountainous sections there is* a regular con- 

 densation of vapor, and the rains fall lighter 

 and in a longer space of time. 



Some of the principles involved in evapora- 

 tion and filtration, are given by Mr. G. in the 

 following paragraphs : 



When the frost leaves the ground in the 

 spring it is 'full of water, and a cubic foot of 

 this saturated earth is to water in its specific 

 gravity as five to three ; dried to the moisture 

 suitable to have seed put in it, it loses one- 

 twelfth of its weight ; when perfectly dried it 

 loses one-third. 



Mr. Dalton, in makinghis experiments, came 

 to the conclusion that when it had lost one- 

 sixth of its weight by drying, it was not too 

 dry to support vegetation. When it had lost 

 two-ninths it appeared like top soil in summer. 



Hence every foot of earth in depth, so satu- 

 rated, contains seven inches of water, and it 

 may part with a quarter of its water, or even 

 one-half, and not be too dry for supporting ve- 

 getation. This is the fund of water with 

 which we start in the spring — say three inches 

 in depth, within one foot of the top of the 

 ground. Boots of plants go down lower than 

 this if the soil is mellow and not flooded with 

 water. 



Mr. Dalton 7 s experiments, made with a cy- 

 lindrical vessel, ten inches in diameter, three 

 feet deep 7 filled with gravel, sand, and soil — 

 having a discharge pipe at the bottom, by 

 which to measure the quantity of water that 

 runs off, and which gave perfect drainage — the 

 top of the soil being covered with grass, the 

 whole buried so that the top was even with 

 the ground, shows that earth that is moderate- 

 ly moist will take up three inches of water 

 without carrying it beyond the point of satu- 

 ration. This amount had in the preceding dry 

 month been taken up by the plants and evap- 

 orated, and, without making the soil too dry, 

 had so drawn upon it that it could imbibe 

 three inches, .which fell in four days. 



Ordinary plowing does not bring into use 

 more than six inches in depth of soil ; extra- 

 ordinary ploughing may reach as low as one 

 foot. Subsoiling and trenching to the depth 

 of three feet would give to the plants all that 

 Mr. Dalton claims for his experiments. Where 

 ground is cultivated only six inches deep, it 

 only holds, subject to the purposes of vegeta- 

 tion, (if no account is made of water rising 

 up through the hard earth beneath,) one inch 

 and a half of water. If cultivation goes down 

 one foot the quantity of available water is dou- 

 bled. If the soil is broken up still deeper, 

 though it may be that the roots of the plants 

 may not go down beyond a foot, yet the water 

 from lower down will rise up by capillary at- 

 traction, and supply the evaporation from the 

 superior parts of the soil. So it results that 

 while one foot of earth will hold for the uses 

 of vegetation three inches of water, three feet 

 will hold so much that it can part (without be- 

 coming too dry,) with three inches, and then 

 receive in the course of a four-clays' rain ano- 

 ther three inches, without overflow or'discharg- 

 ing from the drains beneath. 



It will be noticed that in the estimates com- 

 prised in the last paragraph, no account is made 

 of water rising from the earth below the depth 

 of cultivation. Now it is evident that wheth- 

 er water will rise from below this or not, de- 

 pends on the condition of the underlying stra- 

 ta. It is well known that some soil is natu-, 

 rally just in that state which favors capillary 



