Whether that oil was produced from animal or vegetable substances, appears, even now, a matter of dispute. Some naturalists suppose that vast numbers of oil-giving creatures had been assembled in the districts in which these oil wells are now found, and the oil was pressed out of them by a superincumbent weight of rock. Others assert that the same result might be produced from a vast mass of oil-giving vegetation having been crushed by a similar process. Be that as it may, in several parts of the States, as well as in Canada, enormous pits exist full of this curious oil. It is obtained by boring in the ground in those spots where the oil is likely to be found. Often, however, the speculator, after spending time and capital in the experiment, finds that no oil appears at his call. In some spots, where it was first discovered, after the boring was completed, some hundreds of tons flowed up so rapidly, that it was difficult to find casks sufficient to preserve the produce. The whole region round is impregnated with the odour of the oil. Long teams of waggons come laden with casks of oil on the roads approaching the wells. Sheds for repairing the casks, and storing the oil, are ranged around. Every one gives indubitable signs by their appearance of their occupation, while rock-oil, as it is called, is the only subject of conversation in the neighbourhood. MAMMOTH TREES AND CAVERNS OF CALAVERAS. Gigantic as are the trees found in many of the eastern forests of America, they are far surpassed by groves of pines discovered a few years back in the southern parts of California. They are found in small groves together--in some places only three or four of the more gigantic in size; in others, as many as thirty or forty, one vying with the other in height and girth. In one grove, upwards of one hundred trees were found, of great size, twenty of which were about seventy-five feet in circumference. One of these trees, of greater size than its companions, was sacrilegiously cut down. Its height was 302 feet, and its circumference, at the ground, 96 feet. As it was impossible to cut it down, it was bored off with pump-augers. This work employed five men for twenty-two days. Even, after the stem was fairly severed from the stump, the uprightness of the tree and breadth of its base sustained it in its position, and two days were employed in inserting wedges and driving them in; but at length the noble monarch of the forest was forced to tremble, and then to fall, after braving the battle and the breeze for nearly three thousand winters.