Vol. XXTT. No. 5.] 



POPULAR ■ SCIEN"CE N"EWS. 



71 



J^ome, iFarm, anD Garten. 



THE CHEMISTRY OF THE DAIRY. 

 Milk, the most important of all dairy prod- 

 ucts, is in many respects ^ perfect food, in- 

 asmuch as it contains representatives of all 

 the substances which go to make up the ani- 

 mal frame. It is principally composed of 

 water, butter, milk-sugar, casein, and soluble 

 and insoluble inorganic salts. The amount of 

 the principal constituent, water, is very vari- 

 able, even from legitimate causes, but may be 

 said to average from eighty-five to ninety per 

 cent. 



Although to the unaided ej'e milk appears to 

 be a homogeneous white fluid, the microscope 

 shows it to consist of a clear liquid, in which 

 are suspended numerous globules, which make 

 it opaque. These globules consist of milk-fat, 

 or butter, and eacli one is surrounded by a very 

 thin covering, or membrane. When they are 

 violently agitated, as in churning, these mem- 

 branes are broken, and the globules of butter 

 cohere together into larger masses. The for- 

 mation of the butter is, to some extent, depend- 

 ent on the temperature ; and in old times, when 

 the butter resolutely refused to "come," the 

 trouble was laid to the witches, and a red-hot 

 horseshoe was dropped into the churn, which 

 served the double purpose of frightening away 

 the witches and heating the cream. 



Cream is the lighter portion of the milk, 

 which rises to the surface upon standing. It 

 contains a large proportion of the fatty matter, 

 and is collected and saved for churning. The 

 buttermilk remaining after churning contains 

 about one-fourth of the fatty matter. 



Pure butter is principally a mixture of two 

 fats, known as margarin and olein, with smaller 

 quantities of butyrin, caproin, and caprin. 

 These fats are all analogous to each other, 

 margarin having the symbol C^^Hj^.O,. It is 

 a compound of margaric acid and glycerine, 

 and the margaric acid in turn is probably a 

 mixture of stearic and palmitic acids. These 

 fats are practically identical with those formed 

 in the body of the animal, from which the well- 

 known butter substitute, oleomargarine, is 

 made. The principal chemical difference be- 

 tween the two articles is the lack of the buty- 

 rin, caproin, etc., in the artificial product ; but, 

 as far as healthfulness is concerned, one is as 

 good as the other. In fact, a good article of 

 oleomargarine is preferable to the poorer grades 

 of butter. 



Fresh milk, when chemically tested, is found 

 to be slightly alkaline, and this alkali serves 

 to hold in solution a very important substance 

 called casein, which is the basis of cheese. If 

 a little vinegar or other weak acid is added to 

 milk, this substance separates out in the form 

 of curd. The insoluble pellicle which forms 

 on the surface of boiling milk is due to this 

 substance. When milk sours naturally, lactic 

 acid is formed, which neutralizes the alkali, 

 and the casein separates. It also has the 

 peculiar property of being precipitated by the 

 action of rennet, or the mucous membrane of 

 the stomach of the calf. In this case no acid 



is formed ; but the action seems to depend upon 

 the presence of bacteria, or microscopic organ- 

 isms, in the rennet. If the milk is warmed, 

 it separates more readily; hence when milk 

 that has very slightly soured is added to hot 

 tea or coffee, it " feathers " from the separa- 

 tion of the casein. 



Chemically, casein resembles albumen, con- 

 taining less sulphur than that substance. A 

 substance known as legumin, or vegetable cas- 

 ein, is found in peas and beans, which closely 

 resembles that of milk, and is coagulated by 

 rennet in the same way. If, after churning, 

 the casein contained in the buttermilk is not 

 thoroughly removed from the butter, it will 

 induce a fermentation or decomposition, result- 

 ing in the production of certain volatile and 

 offensive acids, and the butter becomes rancid. 

 In the manufacture of cheese the casein is 

 coagulated by rennet, pressed into the desired 

 shape, and allowed to stand and "ripen." 

 The ripening process is a fermentation analo- 

 gous to that produced in rancid butter, and the 

 powerful odor of certain cheeses is due to the 

 same volatile acids. It is only a matter of 

 habit which makes the flavor of cheese agree- 

 able to some persons, while that of rancid butter 

 is repulsive to every one. Some semi-civilized 

 nations, more consistent than ourselves, will 

 only eat butter when sufficiently "high," con- 

 sidering the fresh article tasteless and insipid. 

 The different kinds of cheeses are dependent 

 upon the kind of milk used in their prepara- 

 tion, the richer ones being made from milk 

 containing a larger proportion of cream. Stil- 

 ton cheese is made from a mixture of new milk 

 and cream, Cheddar from new milk alone, 

 Cheshire from milk from which about one- 

 eighth of the cream has been removed, and 

 Dutch cheese from skimmed milk only. 



The other constituents of milk are of minor 

 importance. Milk-sugar is used, to a limited 

 extent, in medicine ; and the inorganic salts, 

 which consist principally of phosphates and 

 chlorides of potash, soda, lime, magnesia, and 

 iron, are only valuable as increasing its value 

 as a food. From the earliest times milk and 

 its products have been recognized as the best 

 possible substances for the nourishment of the 

 human body ; and the results of modern chemi- 

 cal analysis confirm this belief, and show that 

 they are most perfectly designed to produce 

 health, strength, and flesh. 



[Original in Popular Science Newt.] 

 PEAT. 



BY W. J. CHASE. 



Most readers of the Popular Science News, in 

 common with the majority of people, doubtless 

 have a very indistinct notion of what peat is. 

 They probably have, in connection with their read- 

 ing and study of Ireland, often come across the 

 name. Indeed, it is as the fuel of the Irish peas- 

 antry that peat is best known to American readers. 

 But peat-bogs are by no means peculiar to Ireland 

 or to any one country, being found in all cold 

 countries, yet rarely met with nearer the equator 

 than in the temperate zones. 



Peat is vegetation partially decomposed under 

 water, and the process of its formation is con- 



stantly going on all through New England and the 

 northern part of the United States. Almost every 

 fresh- water swamp contains it; often, however, so 

 mixed with sand as to be hardly recognizable. 



There are many different kinds. The two most 

 common in the United States are the black and the 

 red. The black, called also grass-peat, is formed 

 of partially decomposed grasses, and is of very 

 little value, as it possesses no fibre, and crumbles 

 to pieces in the drying. The red, moss, or wood 

 peat, — for it is known by any of these names, — 

 is perhaps not quite so common as the grass-peat, 

 yet it is found in great abundance. It is formed, 

 as its names suggest, of decomposed moss, swamp 

 herbs, and small shrubs. It is this variety of peat 

 which forms the basis of several already large and 

 growing industries. 



Moss-peat varies in color and quality with the 

 depth from which it is taken. At the surface it is 

 red, and gradually shades in color to a light brown, 

 then darker, until finally, at the depth of fifteen or 

 twenty feet, it is so dark a brown as to be almost 

 black. It is not at all uncommon to find deposits 

 of peat thirty feet, and even more, in depth. At 

 these lowest depths it is much more compact, and 

 has an oily, resinous look. In the language of the 

 peat-digger, it is " fat " peat. 



One of the chief characteristics of moss-peat is 

 its fibre, the existence of which it is hard to 

 explain. It is this fibre which makes it possible 

 to cut it into blocks when wet, which retain the 

 same form when dried. On account of this fibre, 

 too, the dried blocks can be handled and sawed 

 like wood. 



A peat-bed which is being worked, with its regu- 

 lar system of main and cross ditches for draining, 

 presents at a little distance the appearance of a 

 huge cake of chocolate cut up into small squares. 



Peat, without other preparation than that of 

 drying in the sun, has been used as a fuel for more 

 than a century and a half in New England even. 

 But the process of sun-drying a block of wet peat, 

 nine-tenths of which, by weight, is water, is too 

 long, and the fuel when thus prepared is too bulky, 

 to be of much practical value. To overcome this, 

 there are at present sevei'al processes. On the 

 shores of Lake Superior, wliere other fuel is scarce, 

 the peat, taken full of water from the bog, is ex- 

 posed to great pressure, which squeezes out the 

 water, and compresses the block into a much 

 smaller bulk. 



By another process the block of peat, when 

 thoroughly dried by artificial heat, is dipped into 

 a bath of petroleum oil, where it is allowed to 

 remain until it has absorbed like a sponge a cer- 

 tain quantity of the fluid. After draining for a few 

 minutes, it is then dipped int« a bath of liquid 

 resin, from which it emerges encased in an air-tight 

 covering of the hardened resin. 



Besides its uses aa a fuel, peat also is valuable as 

 a fertilizer, both for the ammonia it contains and 

 also for the absorbing properties it possesses; and 

 finally, the mossy top layer of the peat-bog is of 

 considerable value as a stall-bedding for horses and 

 cattle. 



THE BIRD-FOOT VIOLET. 



The bird-foot violet, Viola Pedata, is the 

 largest and most conspicuous of our native violets. 

 Utilik* most of the species, it grows in sandy soil, 

 and likes dry, sunny places. It is really a flower 

 of the woods, growing on their edges, in sandy 

 roads, and on hillsides in the vicinity of woods. 

 It is always associated in my mind with the white 

 birch, for it is in full blossom at about the time 

 when these trees have just come out in their bright, 

 straight-veined, taper-pointed leaves; and wherever 

 I have found them, there were always birches close 



