Page:Hardwicke's Science-Gossip - Volume 1.pdf/166

Leaving Launceston by the western road, and taking our way over Windmill Hill, a pleasant walk of about a mile and a half brings us to a little valley, through which a stream pleasantly ripples along; green fields descend to the water's edge on the one side and the wooded slopes of Landrake rise on the other. Crossing the water by a rustic bridge, and mounting a rather hilly bit of road, by the side of the wood, we turn in through a gate on the right, and find ourselves in an old quarry, known as the Upper, Eastern, or Landrake Quarry, and one of three on the same range, which lays bare to us those peculiarly constituted rocks known as the Petherwin beds, rendered familiar to us by the labours of some of our most eminent geologists.

This quarry is a favourite retreat of ours; many happy hours have we spent in the old place, making the rocks ring to the sound of our hammer—to the amazement, and no doubt the amusement, of the cottagers below and occasional passers-by, who whisper "I wonder what he's about," and no doubt put us down as an eccentric individual, who has taken to stonecracking to ease his troubled mind.

On hammering away at the shales on either side of the valley, we are not long in discovering a marked distinction between the two; those on the Landrake side being fossiliferous, while those on the Launceston side are not so.

Associated also with the fossiliferous shales are irregular bands and nodules of limestone. Formerly much limestone was raised and burnt there, but now the kiln is in ruins, and the lace quite deserted: the geologist therefore who in these latter days happens to visit Landrake Quarry will find no quarryman to apply to for fossils, but must depend entirely on his own perseverance and skilful use of his hammer. The place is, however, well worth a visit; for a suite of very interesting fossils are to be obtained there. Let us endeavour to give you some idea of the more characteristic forms drawn from our own collection.

Among Polyzoa may be found a pretty species of Fenestella; but, as is the case with all the fossils found in the shale, it is but an impression; notwithstanding, it is beautiful, its slender radiating ribs, connected with transverse bars, giving it the appearance of open network.

Among Actinozoa, a beautiful coral from the limestone, approaching in character to the genus Cyathophyllum, being marked with deep longitudinal striæ.

Among Brachiopoda, two species of Orthis, one Leptæna, and several Spiriferæ. A pretty little shale Spirifera (S. unguicula) is very plentiful in some portions of the limestone, while S. disjuncta is found chiefly in the shale.

The specimens from the shale are all more or less distorted, but those from the limestone are not thus affected.

Among Conchifera, one species each of Pullastra, Cyprecardia, and Pecten.

Among Gasteropoda, Eremphalus is a very characteristic form; but the fossils are generally very imperfect.

Among Caphalopoda, Orthoceras is rather plentiful; several species from the limestone, also two very imperfect specimens of (we believe) Clymenia.

Among Crustacea, one trilobite, which Mr. W. Salter (to whom, through the kindness of Mr. Vicary, the fossil was sent) pronounces to be a variety of Phacops latifrons. The specimen in our possession is very perfect; and as trilobites are not caught every day in the Petherwin beds, we will tell you how we got hold of it. We remember we had sauntered out to the quarry one autumn evening, and had worked away for an hour or more, with but little success, having bagged but a few Spirifers, when just at the bottom of the great rubbish-heap we came upon a few likely-looking stones, and as we carefully examined them, expecting, as Mr. Macawber did, in spite of former reverses, that something would eventually turn up. To our great joy, we espied, what we at once knew must be a part of a trilobite. True, there was but a little bit of his back visible, and that was slightly weather-worn; many perhaps would have passed it by; but we had been hunting for this fellow a long, long time, and at last our labour was rewarded—at last we could cry "Eureka!" The question now was how to make the most of him—how to get him out of his hiding-place—would the crab be crabbed, or would he yield to our gentle persuasions, and come out of his hole?

Tap, tap, very carefully with our hammer; the stone gives way, and his tail is set free again; so—well done, there is one side of his head with one eye quite perfect, every lens beautifully preserved. And now shall we let well alone, or risk one more blow? Hurrah, fortune favours the brave, see a perfect specimen of one of the last of the Trilobites.

The most abundant fossils, especially in the middle quarry, are the Spiriferæ. It is worth while clambering over a few hedges and jumping a few ditches to look at this portion of the beds. For several feet thick the rock is full of them; there they lie impressing one another, and you cannot split a fragment of stone without getting some trace of Spirifera.

Another curious feature connected with the Petherwin fossils is the flattened and contorted appearance they generally present, showing us that at some period of their history they must have been subjected to enormous pressure.

So far we have visited two of the quarries; the third it will be sufficient to mention, as very little is to be got there, and it is by no means at present a