PROFESSOR J. J. MAPES'S ADDRESS. 601 



when but slightly disintegrated, as when rendered thoroughly 

 pulverulent ? 



We have all observed that when cold surfaces are presented 

 to the atmosphere, even during the warmer days of summer, 

 that drops of water are condensed upon them. Thus a pol- 

 ished piece of steel, wiped dry before its removal from an ice 

 house, will, on being placed even in the direct rays of the sun, 

 be suddenly covered with drops of water, before its reception 

 of heat causes reevaporation. Must not, therefore, a soil 

 ploughed to sufficient depth to enable the atmosphere to circu- 

 late among the cooler particles, be continually the recipient of 

 moisture from the atmosphere ? If the land is dry, must not 

 the missing moisture be resident in the atmosphere above, and 

 will it not be received and retained by deeply disintegrated 

 soils ? Do not crops withstand drought on deeply disentegra- 

 ted soils, while on those ploughed to a less depth they suffer for 

 want of sustenance ? The necessity of moisture in the soil, 

 as the solvent^ of food for plants, must be evident; for rest 

 assured that plants do not, by any mechanical action, disinte- 

 grate the ultimate particles of manure ; they only enter the 

 plant after solution in water, or after assuming a gaseous 

 form, and enter water in that state. Such solutions then enter 

 the roots of plants, and from their leaves are given off the aque- 

 ous portions, leaving the solid residue to complete the organism 

 of the plant. 



Why do our fields require reploughing ? Is it not because 

 the falling rains lubricate the surfaces of particles, causing the 

 earth to settle to a more compact form ? Is it not to overcome 

 the settling of one season, that we plough the soil the next ? 

 Does not the oxidation of the surfaces of particles from atmos- 

 pheric influences, roughen them, and thus prevent them from 

 so readily settling to a compact form ? 



In the exhibition of to-day, we have witnessed ploughs of a 

 most superior workmanship — surfaces polished to a degree not 

 known to our forefathers — the configuration mathematically 

 in accordance with the requirements of the instrument, and 

 with an equi-libration of the parts so disposed as to place 

 strength where needed, and to insure the greatest degree of 

 lightness. No longer is the ploughman called upon to waste 

 his strength in overcoming the faulty shape of his plough. It 

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