Others there are, that go further and say, that one may every where distinguish the Water of the Lake from that of the Rhone: But the Fishermen will not allow this, but assert, that there is no other Mark than those lately alledged, viz. of the Trouts, and the Current; and that the latter of these is alone sufficient, in calm Weather, to observe the Current of the Rhone from the place of his entring the Lake unto that of his going out.
The Water of this Lake commonly begins to Increase about the end of January, or the beginning of February, and continues to do so unto the twentieth of July, and often unto the very Month of August; and then it insensibly decreaseth, so that the Water is less high in Winter than Summer by twelve or fifteen Feet; the Frosts draining the Springs, or rather Freezing the Waters that issue out of them.
About this Increase of the Water there are also different Opinions. 'Tis true, they all believe in general, that the principal cause of the Increase of the Water is the melting of the Snow, and of the Mountainous Ice, that is in the Winter form'd of the Waters of the Springs and Torrents, which the Frost fixeth. This is so true, that when there is much Snow in Winter, the Waters are very high the ensuing Summer. But when great Rains chance to fall in January, then the Snow, not yet being well hardened, melteth on a sudden altogether. And when this melting is not so violent, all the Snow that will melt, melts at the end of May or at the beginning of June; so that, there remaining but the stock of Ice for entertaining the Increase of the Water unto the Month of August, some have thence been induced to say, that this Increase, which amounts, as has been said, to 15 Feet Water generally all over the Lake, is caused by the Herbs, growing, as they pretend, at its bottom in great abundance; and that these Herbs, whilst growing, do force the Water upwards, and dying in Autumn make the Water to sink lower. Which is not satisfactory to me, because there are no Herbs seen upon the Lake, and very little within it, and the Banks being very dry.
Others there are, that will have this Water rarified by the Heat of the Sun, and thereupon swell'd on the Borders, hot Water not being so high in the middle as cold.
This is certain, that all the Rivers and Torrents, that fall into this Lake, carry with them store of Stones and Earth, which may indeed enlarge and raise it: But such an augmentation or rise cannot be sensible but from Age to Age; not to mention, that in Winter, whilst the Water is low, the Stones of the Lakes are carried away for building or fortifying at Geneva.
At the issuing out of the Barres, that form Geneva, on the side of the Lake, are seen in the Water two or three huge Flints, standing out of the Water; the chief of which they call Niton: And the Tradition is, that it formerly was an Altar consecrated to Neptune; there being also a place cut out in the middle, which they take to have been the place for the Sacrifice. On this Flint seven or eight Persons can sit; and sometimes, when the Waters are very low, there are found about it Knives, and Needles as thick as Bodkins of tweeses, and much longer; both of Brass, well enough made, and esteemed to have served for the Sacrifices.
This Lake in serene and calm Weather appears sometimes, and that even before Sun-rising, as if it were made of divers pieces, differently coloured; part of it being Browner than the rest, which seems to be caused by a Breath of Wind passing thorough the Water, coming either from the bottom of the Lake, or from above; tho' others think this gentle agitation to proceed from some Springs that are at the bottom, making the Water shiver above. But that part of the Water, that is not moved, appears as even and smooth as a Looking-Glass, or like Water traced by a Ship. And as for the Colours, they are, in my Opinion, an effect of the neighbouring Mountains, the different Images of which, being confounded in the Water, make an appearance of very pale Colours.
After that the Rhone is entred into the Lake, he retakes not his impetuous course before a quarter of a Mile's distance from its coming forth again, that is, above Geneva. And the nearer he comes to that Town, the more his Bed becomes narrow, and consequently his course more Rapid. Yet this Rapidness hath been in our times once surmounted by Wind, and once by Water. To understand which, you may imagine, that in Geneva there is a streak of Land about an hundred Fathoms long, which divides the Rhone into two parts, passing under four Bridges, then covered with Houses. From the Point of this Isle unto several ranks of Stakes on that side of the Town, there are about a Thousand common Paces. This whole space of Water, which makes the figure of an V (whereof the Isle is the Point, and the Town forms the sides, and the Stakes the empty place of the end) hath been once laid dry by a violent Wind, after this manner. One Day in the Winter of the Year 1645. there arose in the Morning about 9 a clock so furious a Wind, that not only it uncovered the Houses, but also laid dry the Bed of the Rhone above the Bridges, so that many, in the view of all the Town crossed quite over it dry-foot, and one of the Sons of M. D. Aubigny took up some Medals, which he found in his way. This passage was free during an Hours time; at the end of which the River retook its course. At that Season the Water being very low, and a West-Wind, to arrive at Geneva, being pressed by the high Mountains that bring it upon the Town as by the nose of a pair of Bellows; it came to pass, that that Wind did violently bear upon the Water near the said Bars keeping suspended the Water that was beyond, and those Waters, that were beneath, running away downwards by a declivity, and under the shelter of the Houses. Whilst I was scrupling at this Relation, they brought me Gallasius his Commentary upon Exodus, Printed 1560. where 'tis recorded, that the like accident had fallen out at Geneva at the time when that Minister lived there, a South West Wind having made the Rhone to recoil into the Lake, and many People having thereupon passed over dry for an Hours time.
Concerning the other Accident; you may remember, that the River Arve, which is a kind of Torrent falls into the Rhone, about a 1000 Paces beneath Geneva. In the Month of December in the Year 1652. the said Arve did so extraordinarily swell, that not only it over-run its Banks with impetuosity, but also interrupted the course of the Rhone, and forc'd it to re-enter into the Lake for the space of fourteen hours; though some do esteem, that the Arve dis-gorged it self for that time into the Lake, by passing over the Water of the Rhone, which, in their Opinion, continued his course under the Water of the Arve. However the Water was seen at Geneva to re-enter into the Lake.