33 



THE FARMER'S MAGAZINE. 



tion of much ammonia and carbonic acid, agents which 

 play an important part in the modifications of tiie 

 mineral matter of the soil." Now we regret that Mr. 

 Jamieson has not here favoured us witli a corollary 

 upon the summer exposure and " baking- " of fallows — 

 explaining the use of so heating large clods ; the danger, 

 on the other hand, of thus wasting volatile nutriment 

 from ground in a pulverulent state ; and, again, the 

 extent to which the shading of land by different sorts 

 of cropping may account for the benefits of rotations. 



The degrees of cold observed in soils, and the range 

 of their temperature, are next reviewed ; the conclu- 

 sions being, that " the ground, even in this climate, 

 must be subject to a range of temperature of which the 

 recorded observations of thermometers hung in the 

 usual manner give little conception." "The ground 

 at a foot deep in this country appears to be scarcely 

 afifected by frost, unless where it has been loosened up 

 by the plough or spade." " The action of frost upon 

 the raw mineral matter constituting newly-exposed soil, 

 is of the utmost importance. This mineral matter con- 

 sists of the debris of the various rocks which are found 

 in the country, and is, in fact, an aggregation of minute 

 crystals and earthy matter. In each pebble and frag- 

 ment of undecomposed stone these crystals are inter- 

 laced in all directions. Bodies of this nature exposed 

 to the air and moisture absorb water, which enters into 

 the interstices and crevices between the faces of these 

 crystals, or into the pores of the raw clots of earth. 

 Should frost th^n take place, this contained water 

 changes into ice ; and iu go doing, by a well-known 

 law, expands with irresistible force, shivering the sub- 

 stance in which it is lodged into a number of particles, 

 which number is measured by the quantity of 

 crevices or pores into which the moisture and 

 frost have penetrated. So lon^- as the frost lasts these 

 particles are all bound together by the enveloping ice, 

 but immediately when thaw comts they separate and 

 fall down ; then the lump whicli before showed but one 

 surface to the air has a multitude of surfaces, and 

 the atmosphere acts upon it in an infinitely multiplied 

 degree. It will be shown that the property of con- 

 densing some important gases within a porous body is 

 in proportion to the extent of superficies that tlie gas 

 can meet with. The comminution or crumbling down 

 of the particles of the soil is therefore, even in this 

 respect alone, an important feature : the earthy salts of 

 the soil are also thereby more extensively exposed to 

 the action of the atmospheric influences in bringing 

 about beneficial changes in their constitution. The 

 practical importance of this is well-known to farmers, 

 who, in preparing their stubbles for the next season's 

 crop of turnips, or such-like roots, always endeavour 

 to get as great a breadth of land well turned over be- 

 fore the month of December as they possibly can, in 

 order that it may get the full benefit of the winter's 

 frost." We like this elucidation of the manner in 

 ■which variations of temperature effect the disintegra- 

 tion of the soil, and of the uses of such minute sub- 

 division in fertilizing and preparing the soil for plants ; 

 and there is no doubt that all goo:l husbandmen are 



aware of the advantages of a winter weathering for their 

 land. But we wish something had been added upon 

 points not so " well-known to farmers" ; as, for in- 

 stance, the depth to which heat and cold will penetrate 

 with very deep tillage, and the policy of thus admitting 

 the disintegrating agencies far down into the recesses of 

 the subsoil. 



With regard to the other characteristic properties of 

 the solar rays, the history given of the discoveries o» 

 philosophers in separating the calorific rays from the 

 luminous, and the luminous from the chemical, is 

 curious rather than interesting in an agricultural pub- 

 lication. It has long been a question whether the up- 

 turning of soil from burial in darkness to the aclion of 

 the sunbeams, and, again, the covering and concealing 

 of the soil, may not have a considerable share in causing 

 the results which follow exposure and inversion by til- 

 lage, and the hiding of the surface beneath vegetation 

 or coatings of manure. Is it the nature of earth to 

 submit to the chemical changes requisite for supplying 

 plants with nourishment, most readily in the dark ; just 

 as vegetables exert their vital functions most vigorously 

 in the light ? And, if so, can some anomalies in the 

 theory of rotations be cleared up in consequence, and 

 some improvements be suggested in our field practice ? 

 Our author olPers the following information: ''Mr 

 Hunt has collected a long list of those bodies which 

 have been observed to be more or less susceptible of 

 chemical change under the influence of the solar radia- 

 tions, embracing various salts and compounds of silver^ 

 gold, platinum, mercury, iron, copper, manganese, 

 lead, tin, and other less frequent metals ; also combi- 

 nations of phosphorus and ammonia, chlorine and ni- 

 trogen, nitric acid, and many resinous bodies. Gay 

 Lussac and Tiienard observed that hydrogen and chlo- 

 rine combine so rapidly in sunshine as sometimes to 

 explode, although they do not unite at all in the dark, 

 and only slowly in diftused light ; and Dr. Draper, of 

 New York, has stated the remarkable fact that chlorine 

 wliicli has been exposed to daylight or sunshine pos- 

 sesses qualities which are not found in chlorine made 

 and kept in the dark Dr. George Wilson ascer- 

 tained that in darkness dry chlorine may be kept for 

 three years iu contact with colours without bleaching 

 them, but that a few weeks sufficed to produce that 



efifect in sunlight Sulphuretted hydrogen, if 



made dry, and kept iu darkness, does not bleach, but 

 recovers its bleaching power with the assistance of sun- 

 light, and acts also readily if moist. Oxygen was found 

 to be similarly affected, and also, in a fainter degree, 

 carbonic acid. Nitrogen exerts a faint bleaching action 

 under exposure to sunlight, although it has no appre- 

 ciable power in the dark, whether moist or dry. Some 

 of these gases are present in the soil in large quantity, 

 and the atmosphere is composed almost entirely of the 

 last three. The above would show that under sunlight 

 they act with an energy unknown in its absence. Can 

 the conclusion therefore be avoided that, although we 

 are yet in a great measure ignorant of the precise influ- 

 ence it exerts, light doubtless affects in various ways the 

 mutual action of the atmosphere and the soil, and that 



