rushes upwards from them with great velocity, which I suppose proceeds from the pressure of the water in the reservoir, which forces it out.

Caroline. I recollect having once seen a very curious glass, called Tantalus's cup; it consists of a goblet, containing a small figure of a man, and whatever quantity of water you pour into the goblet, it never rises higher than the breast of the figure. Do you know how that is contrived?

Mrs. B. It is by means of a syphon, or bent tube, which is concealed in the body of the figure. It rises through one of the legs as high as the breast, and there turning descends through the other leg, and from thence through the foot of the goblet where the water runs out. (fig. 1. plate XIV.) When you pour water into the glass A, it must rise in the syphon B, in proportion as it rises in the glass; and when the glass is filled to a level with the upper part of the syphon, the water will run out through the other leg of the figure, and will continue running out, as fast as you pour it in; therefore the glass can never fill any higher.

Emily. I think the new well that has been made at our country-house, must be of that nature. We had a great scarcity of water, and my father has been at considerable expense to dig a well; after penetrating to a great depth before water could be found, a spring was at length discovered, but the water rose only a few feet above the bottom of the well; and sometimes it is quite dry.

Mrs. B. This has, however, no analogy to Tantalus's cup, but is owing to the very elevated situation of your country-house.

Emily. I believe I guess the reason.

There cannot

be a reservoir of water near the summit of a hill; as in such a situation there will not be a sufficient number of rivulets formed to supply one; and without a reservoir, there can be no spring. In such situations, therefore, it is necessary to dig very deep, in order to meet with a spring; and when we give it vent, it can rise only as high as the reservoir from whence it flows, which will be but little, as the reservoir must be situated at some considerable depth below the summit of the hill.

Caroline. Your explanation appears very clear and satisfactory. But I can contradict it from experience. At the very top of a hill, near our country-house, there is a large pond, and, according to your theory, it would be impossible there should be springs in such a situation to supply it with water. Then you know that I have crossed the Alps, and I can assure you, that there is a fine lake on the summit of Mount Cenis, the highest mountain we passed over.

Mrs. B. Were there a lake on the summit of Mount Blanc, which is the highest of the Alps, it would indeed be wonderful. But that on Mount Cenis, is not at all contradictory to our theory of springs; for this mountain is surrounded by others much more elevated, and the springs which feed the lake must descend from reservoirs of water formed in those mountains. This must also be the case with the pond on the top of the hill there is doubtless some more considerable hill in the neighborhood which supplies it with water.

Emily. I comprehend perfectly, why the water in our well never rises high: but I do not understand why it should occasionally be dry.

Mrs. B. Because the reservoir from which it flows, being in an elevated situation, is but scantily supplied with water; after a long drought, therefore, it may be drained, and the spring dry, till the reservoir be replenished by fresh rains. It is not uncommon to see springs flow with great violence in wet weather, and at other times be perfectly dry.

Caroline. But there is a spring in our grounds which more frequently flows in dry than in wet weather: how is that to be accounted for?

Mrs. B. The spring probably comes from a reservoir at a great distance, and situated very deep in the ground: it is, therefore, some length of time before the rain reaches the reservoir, and another considerable portion must elapse, whilst the water is making its way from the reservoir to the surface of the earth; so that the dry weather may probably have succeeded the rains before the spring begins to flow, and the reservoir may be exhausted by the time the wet weather sets in again.

Caroline. I doubt not but this is the case, as the spring is in a very low situation, therefore the reservoir be at a great distance from it.

may

Mrs. B. Springs which do not constantly flow, are called intermitting, and are occasioned by the reservoir being imperfectly supplied. Independently of the situation, this is always the case when the duct or ducts which convey the water into the reservoir are smaller than those which carry it off.

Caroline. If it runs out faster than it runs in, it will of course sometimes be empty. And do not rivers also derive their source from springs ?

Mrs. B. Yes, they generally take their source in mountainous countries, where springs are most abundant.

Caroline. I understood you that springs were more rare in elevated situations.

Mrs. B. You do not consider that mountainous countries abound equally with high and low situations. Reservoirs of water, which are formed in the bosom of mountains, generally find a vent either on their declivity, or in the valley beneath; while subterraneous reservoirs formed in a plain, can seldom find a passage to the surface of the earth, but remain concealed, unless discovered by digging a well. When a spring once issues at the surface of the earth it continues its course externally, seeking always a lower ground, for it can no longer rise.

Emily. Then what is the consequence, if the spring, or I should now rather call it a rivulet, runs into a situation, which is surrounded by higher ground.

Mrs. B. Its course is stopped, the water accumulates, and it forms a pool, pond, or lake, according to the dimensions of the body of water. The lake of Geneva, in all probability, owes its origin to the Rhone, which passes through it: if, when this river first entered the valley, which now forms the bed of the Lake, it found itself surrounded by higher grounds, its waters would there accumulate, till they rose to a level with that part of the valley where the Rhone now continues its course beyond the Lake, and from whence it flows through valleys, occasionally forming other small lakes till it reaches the sea.

Emily. And are not fountains of the nature of springs?