The Grindstone.
Being on the subject of jaws and teeth as a mode of breaking to pieces objects which are placed between them, we will take those implements which grind to powder, or “triturate,” instead of breaking or flattening.
From the very earliest ages, and as soon as man had begun to discover the “staff of life,” the art of grinding naturally assumed an ever-increasing importance.
The first and most primitive mode of grinding corn and converting it into meal was that which was followed by Sarah, when she welcomed her husband’s guests, which we know, from internal evidence, was followed by the uncivilised races who formerly inhabited this island, and by many semi-savages of the present day.
Nothing could be simpler than the machinery used, and nothing could cause a greater waste of muscular power. Two stones were employed, a large one upon which the grain was placed, and a smaller which was held in the hands, and used for grinding the corn to powder, just as the painters of the last century used to grind their colours. The Kafirs of Southern Africa use this simple mill, and so exactly do they keep unconsciously to the customs of long-perished natives, that if one of their mills were buried for a few years and dug up again, it might be mistaken for one of the ancient “querns.” As the stone held in the hand was rounded, it naturally wore a rounded hollow in the lower stone, and this made the process of trituration easier. Perhaps some of my readers may have noticed that when a chemist makes up a prescription, and is obliged to reduce one of the ingredients to powder, he always does so by rubbing, and not by pounding, as is generally believed. He works the pestle round and round the mortar with a kind of twisting motion, and thus obtains a powder much too fine to have been produced by any amount of pounding.
The labour of this operation is necessarily very severe, and therefore the Kafir of the present day, as did his predecessors of the long-lost races, declines to do it himself, but hands it over to the women. In Palestine, as in other parts of the world, a simple mill has been invented, which takes away much of the labour, and, above all, releases the grinder from the obligation of leaning with her fall weight upon the upper stone. In this mill the stones are similar. The upper is moved backwards and forwards round a pivot, and the grain is passed between them by means of a conical aperture in the upper stone, which answers the purpose of our “hopper.”
In order to work this mill, two women are required, sitting opposite each other, with the mill between them, holding the same handle, and assisting each other in turning the stone backwards and forwards. No one who has not seen this operation can fully appreciate the force of the saying that “two women shall be grinding at the mill; the one shall be taken, and the other left.”
It is worthy of remark that, even at the present day, the custom of grinding corn is carried out in Palestine as it was so many centuries ago, and that it is repeated in Southern Africa among the Kafir tribes. In both parts of the earth the first sound of early morning is caused by the millstones of the grinding women, and the amount and duration of the noise afford a sure test of prosperity. Cessation of the millstones signifies adversity and a thin population, as has been said by a writer who lived not very far from three thousand years ago. Speaking of tribulation, he mentions that “the grinders cease because they be few, and that the doors shall be shut in the streets when the sound of the grinding is low.”
After awhile improvements were gradually introduced into the business of grinding, not the least of which was covering its surface with ridges, instead of leaving it entirely smooth, as it had been formerly. Millers of the present time know the value of these ridges, and the additional grinding power which this “facing” gives to a stone. One of these stones is represented in the illustration, so as to show the system on which the ridges and grooves are constructed.
Now, passing from Art to Nature, we find that the whole system of the millstone, its movement and its ridged surface, existed in the times when man had not yet come upon earth.
The reader is probably aware that among the tooth-bearing animals there are three types of teeth. First come the incisors, or cutting teeth, which occupy the front of the jaw, and find their fullest development in the rodent animals, such as the beaver, the squirrel, the rabbit, and the rat. Next them come the canine or piercing teeth, which are so highly developed in all the cat tribe. Lastly, there are the molar or masticating teeth, so called from a Latin word signifying a millstone, because their office is to grind food.
As it is with these last that we have now to treat, we will say nothing about the others.
The molar teeth find their greatest development in the Elephant, the structure of whose molars is exactly like that of our modern millstones. There is certainly one very great difference. When the surface of a millstone is rubbed away, the stone must be re-faced, and sooner or later is worn out altogether, and must be replaced with a new one. This, however, is not the case with the Elephant’s molar teeth, which not only keep their facing perfectly sharp, but have the faculty of renewing themselves as fast as they are worn away.
How these important objects are attained we shall now see.
If the reader will refer to the upper left-hand figure of the illustration, he will see that its surface is for the most part round, with irregularly oval figures, close and thick at one end, and almost disappearing at the other. These are the “facings” of the Elephant’s tooth, and they are formed as follows:—
The tooth, which is of enormous size, is not solid, but is composed of a number of plates laid side by side, like a pack of cards when set on their edge. Each of these plates is composed of a hard external layer of enamel, and an internal layer of comparatively soft bony matter. A slice of badly made toast affords a familiar parallel, the half-charred outside representing the enamel, and the soft, sodden interior being analogous to the bony matter. In order to show the arrangement of these plates, a side view of part of the tooth is given on the same illustration. Sometimes, when the teeth of fossil elephants are discovered, these plates all fall asunder, the material which connected them having been dissolved away in the earth.
When, however, we look upon the upper surface of a recent tooth, we see it present the appearance which is shown in the illustration. The elongated oval marks are the edges of the hard enamel plates, while the spaces between them are filled with the soft bony matter. It will be evident, then, that if two teeth such as these be in opposite jaws, and perform the task of grinding food, their surface will always be well “faced.” Owing to the different hardness and density of the enamel and bony substance, the latter will wear away with comparative rapidity, leaving the former to project slightly, and thus to preserve the facing of the natural mill.
This is, indeed, but a modification of the beautiful animal mechanism which keeps the teeth of a rodent animal always sharp, and always bevelled off at the proper angle. If we could invent some plan whereby, in our millstones, we could make the facing of much harder material than the stone, we should make an advance in the miller’s art that would render the millstones of the future as far superior to those of the present as are our present millstones to the hand “quern” of the Kafir women.
Yet another improvement has to be made. Would it be possible to construct a millstone which should not only retain its facing, but possess the power of renewing itself in proportion as it is worn out? This property is found in the Elephant’s tooth, and the illustration will give a tolerably good idea of the simple and beautiful mechanism by which it is brought into operation.
The tooth, instead of being one solid mass, consists, as I have already stated, of a series of plates set side by side. These plates are so constructed that they are more worn away in front than behind. In proportion as they are worn, a new tooth is built up behind the old one, and gradually pushes off the old one. Now, if we could only construct millstones with such properties, we should possess an absolutely perfect instrument.