The history of salt

by Evan Marlett Boddy

The Batrachians, a class of animals allied to the reptiles, but undergoing a peculiar metamorphosis, have an antipathy to salt, and consequently cannot live in salt water; it is death to them sooner or later.

We cannot say that reptiles, as a rule, frequent fresh water in preference to salt, some being found only in sea-water, and in those parts of the ocean where there is a greater quantity of saline matter than in others. There is the marine Chelonia, for instance, commonly known as turtles (Chelones); one sub-group, the common green turtle, so well known for its palatable qualities, is composed of species altogether herbivorous, and of gregarious and innocent habits, “These animals may be seen in herds at the bottom of the sea, quietly browsing on the weeds growing there. Sometimes they enter the mouths of large rivers, and are occasionally seen to make their way ashore, apparently in search of food.”[51] Like the salmon, it is a habitat of both fresh and sea water, though under different conditions; one frequents fresh-water for food, the other for breeding. Another sub-group comprises turtles of carnivorous habits, active, and, when attacked, fierce; such is the loggerhead turtle and the hawksbill; the latter is the animal which furnishes the arts with the elegant substance called tortoise-shell. There is also a genus of carnivorous habits, called the Sphargis, or coriaceous turtle.

There are likewise the river tortoises (Tryonices), which are conspicuous tenants of the Ganges, the Euphrates, the Niger, the Nile, the Mississippi, and the Ohio. These reptiles are next in size to the turtles, some being three feet long; they are very fierce, and do not even scruple to attack the young alligators. They live principally on fresh-water fish and small reptiles; sometimes they will venture into sea-water in quest of food, though not far, as we may suppose. There are also the Emydes, which are sometimes called fresh-water tortoises, sometimes marsh tortoises, which are of many different species. They haunt lakes, marshes, and small rivers in Asia, Africa, and Australia, but more particularly America, where the proper habitat is represented. In the North American rivers there is found the Emysaura serpentina, which has a large head and crocodilian tail; it feeds on fishes and small birds. Another species, called Chelys fimbriata, or Matamata, belongs exclusively to the rivers of Guiana.

We thus see that the Chelonia, which are remarkable for the box-like case in which most of them are enclosed, are inhabitants of the sea, while their near relations, the tortoises, are only partially aquatic in their habits.

Reptiles are therefore neither land, sea-water, nor fresh-water animals, if we view them as a whole; but if we divide them into orders, we shall be able to see at once which are fresh-water, which are terrestrial, and which are inhabitants proper of the sea. Firstly, there is the Amphibia (doubled-lived), which live and breed in fresh water, such as rivers, lakes, ponds, and ditches, and which are killed if put into salt water. Secondly, there is the Ophidia (snake-like order), which are peculiar to the land, though there is a fresh-water snake in the East Indies, and which the natives will boldly attack with sticks. The Sauria (lizards) next claim our attention. The alligator is a native of North America, and is very abundant in the Mississippi. It is very seldom seen near the mouths of rivers, and in winter it buries itself in the mud, and continues in a torpid state till spring. Then there are the crocodiles, which are natives of Africa, the West Indies, and America. Their habits are somewhat similar to those of the alligator, frequenting the creeks of rivers by night in search of food; they are sometimes seen near the mouths of rivers, but not as a rule. We have already remarked upon the Testudinata, or the turtle kind.

Reptiles, therefore, either frequent the land or the water; some are purely aquatic, others purely terrestrial, the remainder are both; one order is altogether marine, though frequently they are seen on shore, where they are caught.

Salt water is death to one order, but affords the means of life to another; to yet another order, with but few exceptions, both salt and fresh water are deleterious, and, in fact, death; whilst still another order frequents both elements, just as the chances of obtaining food may direct them.

Such animals as the hippopotamus, the rhinoceros, the tapir, and the elephant, and a few others belonging to the Pachydermata, frequent the banks of rivers and fresh-water lakes, where they wallow in the mud, and now and then, as fancy takes them, splash about in the water; but they, like the crocodile, have never been known, as far as I can gather, to make for salt water, and therefore they are seldom, if ever, seen near the mouths of rivers, or by the coast.

Salt is therefore not avoided, almost as a rule, either by animals or birds; and in those districts where salt lakes are situated (to which interesting fact I have already alluded) are to be invariably seen, not only great numbers of animals, but large flocks of birds of different kinds, showing conclusively that they possess an instinctive preference for those localities where the atmosphere is more or less filled with saline matter, than for those places where it is entirely absent. It is but seldom that animals frequent those spots which are injurious to them; they take good care to avoid them, if possible, and if they detect anything deleterious, whether it be in the air, soil, or water, they migrate to more genial quarters; instinct indicates this necessity, and they accordingly act upon it. It is strange that mere animal instinct should be superior to human reason, and that animal sagacity should be more far-seeing than human forethought! Nothing is more strongly confirmative of this anomaly, if I may call it so, than the partiality which animals entertain for those districts which abound with salt lakes, and the antipathy, or utter indifference, with which some people regard that substance which keeps the body pure, healthy, and, I may say, clean, and which plays such a highly-important part in the animal economy.

In the vegetable kingdom salt is by no means an inconsiderable item, and as an agricultural agent it is most invaluable, though its operation therein varies in a remarkable degree; in small quantities it is injurious only to a few plants, while to some it appears to be beneficial in every way. In moderation it is an excellent manure, especially if the soil is of a sandy nature; but in large quantities it is decidedly pernicious to all plants, without an exception, though unequally so. According to experiments made by Dr. Balfour and other eminent botanists, it appears that a solution of the chloride of sodium does not act so deleteriously as solutions of other inorganic substances, and the same effect is observable with a solution of the phosphate of soda: the strength of these solutions, we are told, varied from half a grain to five grains to the ounce of water; the sodium combined with the chlorine forming the chloride of sodium, and with the oxygen forming soda; the potassium, combined with the chlorine, forming the chloride of potassium, and with the oxygen forming potassa. The combinations take place, according to Johnston, in the living plants owing to the natural affinities of these inorganic substances.