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The marrowy organisms, with skins that shed water like the backs of ducks, with smooth surfaces neatly padded beneath, and velvet linings to their singing-pipes, are not so common among us as that other pattern of humanity with angular outlines and plane surfaces, and integuments, hair like the fibrous covering of a cocoa-nut in gloss and suppleness as well as color, and voices at once thin and strenuous, acidulous enough to produce effervescence with alkalis, and stridulous enough to sing duets with the katydids.
The strongest and most soluble bases are the alkalis soda, potash, and ammonia. You all know, probably, that a drop of vitriol allowed to fall on a black felt hat will stain that hat red if the hat has been dyed with logwood black; and if you want to restore the black, you can do this by touching the stain with a drop of strong ammonia.
I can inoculate with various liquids acids, weak nitric acid, alkalis, ammonia, neutral bodies, spirits of wine, essence of turpentine and obtain conditions similar to those of the victims of the predatory insects, that is to say, inertia with the persistence of a dull vitality betrayed by the movements of the mouth-parts and antennae.
Nature, not education, rendered Faraday strong and refined. A favourite experiment of his own was representative of himself. He loved to show that water in crystallizing excluded all foreign ingredients, however intimately they might be mixed with it. Out of acids, alkalis, or saline solutions, the crystal came sweet and pure.
I have already told you that acids are characterised by what we term an acid reaction upon certain vegetable and artificial colours, whilst bases or basic substances in solution, especially alkalis, restore those colours, or turn them to quite another shade; the acids do the one thing, and the alkalis and soluble bases do the opposite.
Following is a list: "Ashes of wolf's skull, stag's horn, the heads of mice, the eyes of crabs, owl's brains, liver of frogs, viper's fat, grasshoppers, bats, etc., these supplied the alkalis which were prescribed. Physicians were accustomed to order doses of the gall of wild swine. It is presumed the tame hog was not sufficiently efficacious.
This power of charcoal also extends to gases, and to certain noxious dissolved organic impurities, but it is never safe to rely too much on such filters, since the charcoal can at length become charged with impurities, and gradually cease to act. These filters need cleaning and renewing from time to time. Properties of Acids and Alkalis.
Observe I give him a very high place but Davy's discoveries are both of more unquestioned originality and more undoubtedly true perhaps I should say, more brought to a close. The alkalis and the principle of the safety lamp are concluded and fixed, the undulation is in progress, and somewhat uncertain as to how and where it may end.
We have now learned that acids are as the antipodes to alkalis or bases, and that the two may combine to form products which may be neutral or may have a preponderance either of acidity or of basicity in short, they may yield neutral, acid, or basic salts. I must try to give you a yet clearer idea of these three classes of salts.
Now, neutral tartrates, citrates, and acetates of the alkalis are found, in their passage through the system, to be changed into carbonates; and to convert a tartrate into a carbonate requires an additional quantity of oxygen, the abstraction of which must lessen the oxygen destined for assimilation with the blood, on the quantity of which the vigorous action of the human system partly depends.
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