known also in the same period to lose both 

 bodily and mental capacity, bj- llie loss of brain 

 and ner\-e, from a want of azotized matter in 

 what they eat. 



As nitrogen in the form of albumen, gluten, or 

 casein must be eaten, and as these compoumis 

 are found in vegetables identically the same as 

 in animals, except in tiieiroutwaid appearance, 

 and as we know thai there is jio other form in 

 whicli niiros-'en can be obtained, we have a key 

 by which we can Knd cxactiy how much of any 

 given food is nece.'ssary to form a given quantity 

 of flesh; at least we can tell the minimum, and 

 caii also lei! the comparative value of different 

 kinds of food. We can no longer dispute about 

 the value of a potato, or say a given weight of 

 potato is equal to the same weight of wheat ; 

 nor can we suppose that rice is equal to its 

 weight of flour from wheat or of meal from oats. 

 They are. no doubt, all valuable in their place, 

 as all circumstances do not demand the same 

 mode of treatment. 



The analysis of the a.shes of plants have fur- 

 ni.shed, also, an important lesson as to the capa- 

 cities of soils. If a plant requiring a great deal 

 of silica be put upon land containing little or none 

 in a soluble state, the plant will, of course die, 

 although the same ground may produce an 

 abundant crop of potatoes, for example, which 

 grow with little. The same may be said of lime, 

 rna?nesia. soda, potash, although, more or less, 

 they are always present. To give an idea of 

 the variety in this respect, presented by the 

 more common crops, a table is here added : 



Salts of Pot- Lime and 

 Silica Plants. ash and Soda. Magnesia. Silica. 

 Oat-straw, with seeds.. :«.f)0 4.00 62.00 



Wheat-straw 22 7.20 61:05 



Bf,rl<'y-straw, with seedsl9 25.70 55.03 



Rye-straw 18.65 16.52 63.89 



Lime. 



Pea-straw 27.82 63.74 7.81 



Potato, (herb) 4.20 .59.40 36.40 



Meadow clover 39.20 56 4.90 



Poiai5h. 



Turnips 81-60 18.40 



Beet-rcot -.83 12 



rolato..-3 85.81 14.19 



Suntlower 84.30 15.70 



To try to gi-ow any of these plants on a soil void 

 of potash, soda, lime, and magnesia, will of 

 course be a fruitless occupation ; but we may 

 grow tuniip.s and potatoes when we cannot grow 

 corn. Corn requires a great deal of silica, espe- 

 cially for the straw, and a time of fallow is re- 

 quired in .order that a certain porticm should be 

 made soluble by the atmosphere and other agen- 

 cies. To carry out the deductions from these 

 premises, is the business of the farmer ; to eslab 

 lish the premises with respect to individual soils, 

 is that of the chemist. It would be a great advan- 

 tage to the Agriculturist to be able to obtain some 

 idea of the nature of his soil by chemistrj-. A 

 complete analysis is by no means necessary ; a 

 little practice would enable him to make many 

 important ob.servations as to the quantities of cer- 

 tain ingredients, without at any time using a bal 

 ance, except in the first in.«tance ; that is in the 

 amount of soil experimented on. which ought 

 always to be the same. In this case the eye be- 

 comes experienced and its results in general 

 are equal in value to the wci'-'liings of the bal- 

 ance It is true there are difliculties in the way, 

 as even this small accomplishment is not, as we 

 might suppose, easily obtained without some 

 teaching. At least let us hope that the young 

 will not grow old without it. 

 ,'374) 



In looking at his works, we seem almost to 

 have lost sight of the workman ; and, if there 

 be any test of greatness which will stand, it is 

 this : to have done so much, and to have put so 

 many in motion, that he himself need not guide 

 the machine. To govern, the mind of the gov- 

 ernor must be everywhere ; \\ith his sloth all is 

 slothful, with his loss all is lo.st. But to teach 

 men truth, and to make them understand, is to 

 make what can reprodace itself, and form an 

 endless series. 



One of the most novel doctrines of Professor 

 Liebig is that of poisons, contagions, and mias- 

 mata ; and, however dark the subject now is, 

 v^e may expect it to increase and multiply to a 

 great extent. In such mysterious subjects, to 

 make a theorj-w'ith a foundation is a great deed; 

 and the one alluded to explains so much, that it 

 ^viU no doubt be looked on by many as the most 

 beautiful part of his work. It is remarkable 

 that all the ideas which Daltou obtained on the 

 state of atoms, in union and separation, were 

 taken from the mechanical slates of large bodies 

 such as he could weigh and handle. His sim 

 pie explanation seems now self evident ; and 

 we wonder that men .should have thought oth 

 erwise: we wonder also that great men. such 

 as Wollaslon and Davy, should have doubied-- 

 should, in fact, have been unable properly to 

 comprehend it for a long time. A law in me- 

 chanics has suggested a chemical action to Pro 

 fessor Liebig, which promises notmuch less tiian 

 the theorv" of Dalton. '• A molecule, set in niu 

 tion by any power, can impiart its own motion 

 to another molecule with which it may be in 

 contact." "We have seen that ferment or yeast 

 is a body in a state of decompo.sition, the atoms 

 of which, consequently, are in a state of motion 

 or transposition. Yeast, placed in contact with 

 sugar, communicates to the elements of that 

 compound the same state, in consequence of 

 which the constituents of the sugar arrange 

 themselves into new and simpler forms — name- 

 ly, into alcohol and carbonic acid. 



" In these new compounds the elements are 

 held together by stronger aflinities than they 

 were in the sugar, and therefore, under the con- 

 ditions in which they were produced, farther 

 decomposition is arrested. W^e knov/ also that 

 the elements of the sugar assume totally differ- 

 ent arrangements, when the substances ■which 

 excite their transposition are in a different state 

 from the yeast just mentioned. Thus, when su- 

 gar is acted on by rennet, or putrifying vegeta- 

 ble juices, it is not converted into alcohol and 

 carbonic acid, but into lactic acid, mannit, and 

 gum, or into butyric acid." 



Yeast is a product of the decomposition of 

 gluten ; it passes into a second stage, in contact 

 with water, gives to the .sug;ir an excitement to 

 decompose, and, if any gluten be pre.sent, it 

 causes it to undergo the first stage of decompo- 

 sition, and to pass into j-east. These conditions 

 are found in the fermentation of beer, and, whilst 

 one portion of the gluten is disappearing, an- 

 other portion is being produced from the gluten. 



That a body in a state of decomposition can 

 communicate' to another body a shnilar state 

 seems, from these and many similar facts, to be 

 proved ; or, in other words, that a body in chem- 

 ical motion acts in an analogous manner on sur- 

 rounding particles to a body ui mechanical mo- 

 tion. We see lliat, in the action of the yea.st, 

 the force is not exhausted, as, if material be i)re- 

 sent, a second portion is formed whicli can. of 

 course, do the same work, and the end can be 



