tion of the natural order has produced, as such contravention always must produce, a certain confusion and false movement, of which we are now beginning to feel, in almost every direction, the inconvenience. In all directions our habitual 5 causes of action seem to be losing efficaciousness, credit, and control, both with others and even with ourselves. Everywhere we see the beginnings of confusion, and we want a clue to some sound order and authority. This we can only get by going back upon the actual instincts and forces which 10 rule our life, seeing them as they really are, connecting them with other instincts and forces, and enlarging our whole view and rule of life.

Thomas Henry Hurley.

1825-1895.

ON A PIECE OF CHALK.

(1868.)

If a well were to be sunk at our feet in the midst of the city of Norwich, the diggers would very soon find themselves at work in that white cubstance, almost too soft to be called rock, with which we are all familiar as chalk."

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Not only here, but over the whole county of Norfolk, the 5 well-sinker might carry his shaft down many hundred feet without coming to the end of the chalk; and on the sea-coast, where the waves have pared away the face of the land which breasts them, the scarped faces of the high cliffs are often wholly formed of the same material. Northward the chalk 10 may be followed as far as Yorkshire; on the south coast it appears abruptly in the picturesque western bays of Dorset, and breaks into the Needles of the Isle of Wight; while on the shores of Kent it supplies that long line of white cliffs to which England owes her name of Albion. Were the thin 15 soil which covers it all washed away, a curved band of white chalk, here broader and there narrower, might be followed diagonally across England from Lulworth in Dorset to Flamborough Head in Yorkshire-a distance of over 280 miles as the crow flies. From this band to the North Sea on the 20 east, and the Channel on the south, the chalk is largely hidden by other deposits; but except in the Weald of Kent and Sussex it enters into the very foundation of all the southeastern counties.

Attaining, as it does in some places, a thickness of more 25 than a thousand feet, the English chalk must be admitted to be a mass of considerable magnitude. Nevertheless it

covers but an insignificant portion of the whole area occupied by the chalk formation of the globe, which has precisely the same general characters as ours, and is found in detached patches, some less and others more extensive than the Eng5 lish. Chalk occurs in northwest Ireland; it stretches over a large part of France, the chalk which underlies Paris being, in fact, a continuation of that of the London basin; runs through Denmark and Central Europe, and extends southward to North Africa; while eastward it appears in the 10 Crimea and in Syria, and may be traced as far as the shores of the Sea of Aral, in Central Asia. If all the points at which true chalk occurs were circumscribed, they would lie within an irregular oval about 3,000 miles in long diameter -the area of which would be as great as that of Europe, and 15 would many times exceed that of the largest existing inland sea, the Mediterranean.

Thus the chalk is no unimportant element in the masonry of the earth's crust, and it impresses a peculiar stamp, varying with the conditions to which it is exposed, on the scenery 20 of the districts in which it occurs. The undulating downs. and rounded coombs, covered with sweet-grassed turf, of our inland chalk country, have a peacefully domestic and muttonsuggesting prettiness, but can hardly be called either grand or beautiful. But on our southern coasts the wall-sided cliffs, 25 many hundred feet high, with vast needles and pinnacles standing out in the sea, sharp and solitary enough to serve as perches for the wary cormorant, confer a wonderful beauty and grandeur upon the chalk headlands. And in the East chalk has its share in the formation of some of the most ven30 erable of mountain ranges, such as the Lebanon.

What is this wide-spread component of the surface of the earth? and whence did it come?

You may think this no very hopeful inquiry. You may not unnaturally suppose that the attempt to solve such prob35 lems as these can lead to no result save that of entangling the inquirer in vague speculations, incapable of refutation. and of verification. If such were really the case, I should have selected some other subject than "a piece of chalk" for

my discourse. But in truth, after much deliberation, I have been unable to think of any topic which would so well enable me to lead you to see how solid is the foundation upon which some of the most startling conclusions of physical science rest.

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A great chapter of the history of the world is written in the chalk. Few passages in the history of man can be supported by such an overwhelming mass of direct and indirect evidence as that which testifies to the truth of the fragment of the history of the globe which I hope to enable you to read with 10 your own eyes to-night. Let me add that few chapters of human history have a more profound significance for ourselves. I weigh my words well when I assert that the man who should know the true history of the bit of chalk which every carpenter carries about in his breeches-pocket, though 15 ignorant of all other history, is likely, if he will think his knowledge out to its ultimate results, to have a truer and therefore a better conception of this wonderful universe, and of man's relation to it, than the most learned student who is deep-read in the records of humanity and ignorant of those 20 of Nature.

The language of the chalk is not hard to learn, not nearly so hard as Latin, if you only want to get at the broad features of the story it has to tell; and I propose that we now set to work to spell that story out together.

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We all know that if we "burn" chalk the result is quicklime. Chalk, in fact, is a compound of carbonic-acid gas and lime, and when you make it very hot the carbonic acid flies away and the lime is left. By this method of procedure we see the lime, but we do not see the carbonic acid. If, on 30 the other hand, you were to powder a little chalk and drop it into a good deal of strong vinegar, there would be a great bubbling and fizzing, and, finally, a clear liquid, in which no sign of chalk would appear. Here you see the carbonic acid in the bubbles; the lime, dissolved in the vinegar, van-35 ishes from sight. There are a great many other ways of showing that chalk is essentially nothing but carbonic acid and quicklime. Chemists enunciate the result of all the ex

periments which prove this by stating that chalk is almost wholly composed of "carbonate of lime."

It is desirable for us to start from the knowledge of this fact, though it may not seem to help us very far towards what 5 we seek. For carbonate of lime is a widely-spread substance and is met with under very various conditions. All sorts of limestones are composed of more or less pure carbonate of lime. The crust which is often deposited by waters which have drained through limestone rocks, in the form of what 10 are called stalagmites and stalactites, is carbonate of lime. Or to take a more familiar example, the fur on the inside of a tea-kettle is carbonate of lime; and for anything chemistry tells us to the contrary, the chalk might be a kind of gigantic fur upon the bottom of the earth-kettle, which is kept pretty 15 hot below.

Let us try another method of making the chalk tell us its own history. To the unassisted eye chalk looks simply like a very loose and open kind of stone. But it is possible to grind a slice of chalk down so thin that you can see through 20 it until it is thin enough, in fact, to be examined with any magnifying power that may be thought desirable. A thin slice of the fur of a kettle might be made in the same way. If it were examined microscopically, it would show itself to be a more or less distinctly laminated mineral substance, 25 and nothing more. But the slice of chalk presents a totally different appearance when placed under the microscope. The general mass of it is made up of very minute granules; but imbedded in this matrix are innumerable bodies, some smaller and some larger, but on a rough average not more 30 than a hundredth of an inch in diameter, having a welldefined shape and structure. A cubic inch of some specimens of chalk may contain hundreds of thousands of these bodies, compacted together with incalculable millions of the granules.

The examination of a transparent slice gives a good notion 35 of the manner in which the components of the chalk are arranged, and of their relative proportions. But by rubbing up some chalk with a brush in water and then pouring off the milky fluid, so as to obtain sediments of different degrees of