but omitted by B. and M.; it is about the diameter of the larger crater. The projecting cusp on the right-hand was on the latter occasion very luminous. The two small craters E. and W. of Hyginus are larger

1

2

but in or near the latter crater. I have no note of any other crater W. of Hyginus, but I carry the cleft further than B. and M., turning it, like L., with a bend more S. towards the site of Agrippa b, and then again bending it W. and carrying it on as a very minute line across the N. slope of Agrippa, at a considerable distance from the ring. B. and M. may have seen part of this as the long bank shown (but a little too far N.) in our diagram.

The second great cleft I have seen bordered in all its length, though less distinctly in the portion E. of Silberschlag, by a narrow faint shadow parallel to it on the S., as though on that side at least it had an elevated margin.* I have drawn it as commencing on the N. side of Ariadæus a. Three times it has appeared to me interrupted by the narrow ridge W. of ß, which it divides in B. and M. I have never seen ẞ nor a divided by it; as to a on the other (E.) side of Silberschlag, I am less confident. I may have mistaken it for the ridge N. a little W. of Silberschlag, by which, like Schr., I have seen the cleft entirely intercepted. It has not appeared to me to pass close to the crater opposite Silberschlag as in B. and M., but at a little distance, as in Schr. and L., and the bend at this place is greatly exaggerated by B. and M. The semi-crater form of Schr.'s D I have plainly made out. A little E. of this spot it sends off a very distinct branch to the S.E., which apparently forms a communication with the W. end of the Hyginus cleft, somewhat N. of the point where the latter carries on a branch, already noticed, across the N. slope of Agrippa. I have no note of the small crater at the E. end of this cleft, but I have remarked a very faint narrow dark line continued on from near that spot still further E., towards the end of the Hyginus cleft.

These minutiæ may be of some interest as showing the multiplicity and intricacy of these cracks, and as aids to further study; but the most curious remains to be specified. 1861, April 17, I perceived that the part of the cleft between a and B

* With the great Northumberland Telescope, at Cambridge, aperture 11 in., Breen has seen both banks very plainly, alike in valley and mountain, and has noticed them stretching a short distance into the dark part of the disc.

is double, or rather that in this space are comprised the ends of two clefts not in the same line, but running parallel for a short distance, as is shown in the accompanying very rough

B

sketch. The S. portion, though narrow,

was very evident. As I have found this subsequently confirmed, I would venture to propose an addition to the nomenclature here, and to call the E. portion "the cleft of Silberschlag," as the W. is that of Ariadæus. How so apparent a feature should have escaped all previous observers, and even Schmidt himself, it is not easy to understand; but it proves how much yet remains to be done for the topography of the Moon.

This becomes still more evident with great apertures and high powers, for which many peculiarities here are doubtless reserved. Such was especially my conviction in the use of Mr. Bird's noble 12 in. silvered mirror, 1865, Sept. 5. The illumination was then far too high, but some idea of the scene may be obtained from the fact that the bottom of the first cleft W. of Hyginus was distinctly seen as a grey streak bordered by two parallel bright lines. This was interesting in another respect. The steep banks, as less directly enlightened, should have had a darker appearance, on optical grounds, than the included level space; their opposite aspect must have been due to local colour. On one occasion I thought, in using my 9 in. mirror, that the Silberschlag cleft passed over, not through, a considerable mountain; but the observation was too hasty, and should be repeated.

As to the region of Triesnecker, I have noted several additions. The angular point of meeting, and the minute crater on the slope beneath it, are both set too near the ring by B. and M., and that angle is really the common junction of four clefts; one of which proceeds due S., I know not whether it may be, ill-drawn in their map, or a line of communication with it; another runs as a continuation of ẞ up to the N.W. edge of the great ring: the cleft y, as Breen had previously found, is double, with overlapping ends, like those of the junction between Ariadæus and Silberschlag; and possibly this may be found to be a peculiarity of frequent occurrence. appears, too, to lead directly towards the small crater near its N. end while c, or e (both which letters are affixed in the map to the cleft pointing to the centre of Triesnecker-e has been accidentally misplaced in our diagram), probably passes W. of the little crater E. of Hyginus.

ช

We leave now this curious region with the sincere hope that some of our readers may be induced to make it an object of patient research: a very little experience will show that no

hasty investigation can possibly master its difficulties: many of the clefts are extremely minute, and the shadows, by which alone they can be detected, are in proportion fugitive, so as to require watching, literally, almost from hour to hour, in order to trace their continuation and connection. It would be well, too, to check our results in the opposite illumination, though the large clefts, at least, are not so distinct in the waning moon.

A little way out of our diagram to the N. lies the fine crater Manilius (24) 25 miles in diameter: the broad and peak- and crater-besprinkled ring of which attains in general a luminosity of 8°, and so becomes always a conspicuous object; it may be perceived even in the lunar night, and was one of 's pseudo-volcanoes. The E. side attains 7700, the W. 7500f. (Schr. found 7500 E., 8000 to 9900 W., and the W. wall 2200f. above the plain).

Between Manilius and Menelaus (15), Schr. has represented a very dark spot of an oval form, to which he gave the name Boscovich. L., though he represents it, seems not to have thought it worthy of a name, and has transferred the appellation, without notice (a most unusual procedure with him), to another dark spot half-way between it and Agrippa, where it has been recognized by B. and M., and is shown in our diagram. From Mr. Birt's observations it seems that B. and M. have failed in delineating this region (the old site); Schr. and L. seem to be nearer the present state of the surface, but the dark tone given by Schr. seems either to be visible only under certain circumstances, or to have subsequently faded. In these districts the flat ring-form so common elsewhere, is supplanted by openings, or intermissions among the parallel ridges universally prevalent here, so that two of their sides only are bordered by a rampart. Of this kind is Julius Cæsar, a large steel-grey depression, of only 1° in reflective power at the N. end, becoming as bright as 3° southwards. In its peculiar aspect Chacornac traces the effect of a retreating tidal wave, which he thinks may have penetrated it from the neighbouring sea; and he considers this as one of the many evidences of similar action. Several dark valleys unite it with a similar, but much smaller and not quite so dark, formation at some distance N. On its W. side the true crater Sosigenes, 14m. broad, and, according to Schr., 3700f. deep, intervenes between it and the M. Tranquillitatis: at a little distance E. is the Boscovich of L., and B. and M., another very dark spot of the same kind.

JUPITER'S SATELLITES.

As the planet Jupiter is now conspicuous, though not so high as desirable, the following particulars of his system will

be interesting. Sept. 6th. I. in transit, 7h. 56m. to 10h. 16m., its shadow 8h. 14m. to 10h. 34m. II. ditto, 8h. 26m. to 11h. 18m., its shadow 9h. 2m. to 11h. 54m.-13th. I. in transit, 9h. 40m. to 12h., its shadow 10h. 9m. to 12h. 28m. II. ditto, 10h. 43m. to 13h. 35m., its shadow 11h. 39m. to 14h. 32m. (These two will be beautiful spectacles.)-20th. I. in transit, 11h. 25m. to 13h. 45m., its shadow enters 12h. 4m. II. enters 13h. 2m.-22nd. I. leaves disc 8h. 11m., its shadow 8h. 52m.-29th. I. in transit, 7h. 38m. to 9h. 57m. its shadow 8h. 27m. to 10h. 47m.

OCCULTATIONS.

Sept. 7th. B.A.C. 6292, 6 mag. 9h. 49m. to 10h. 22m.8th. p Sagittarii, 5 mag., 9h. 47m. to 10h. 51m.

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THE FOOD OF THE SALMON.

BY W. HOUGHTON, M.A., F.L.S.

DIFFERENCE of opinion has long prevailed with regard to what constitutes the food of the salmon. As I have lately been examining a large number of the stomachs of this fish, it may interest the readers of this magazine to hear the conclusion at which I have arrived. But let us first of all see what authors have said on this question. The earliest mention of the food of the salmon with which I am acquainted, occurs in Gesner's work "De Aquatilibus," p. 828. Quoting Hector Boëthius, says, "On what food the salmon lives, or whether it lives on any at all, is as yet a doubtful question, since, when disembowelled, the stomach shows nothing but a certain thick fluid." Gesner then adds, "I myself also, whenever I have examined a dissected specimen, have never found anything in the stomach and intestines except a yellowish mucus and particles of white grit. Our fishermen affirm that they never find anything in the stomachs of the large fish, but only in those of the smaller ones; for the larger ones which are known by the name of salmon, live on nothing but water, preferring that which is thick and muddy as being more nutritious. But I have heard from an old and experienced fisherman that the fish, until it is a true salmon, feeds on aquatic lice, but that after spawning it will eat any fish that happens to come in its way; the fisherman said he had frequently found fish in their insides."

Shaw

"Album lapillum." I suspect he means by these words the masses of calcareous crystals so frequently found in the intestines of salmon.

says,

"All fishermen agree that they never find any food in the stomach of this fish. Perhaps during the spawning time they may entirely neglect their food, as the Phocæ, called sealions and sea-bears, are known to do for months together during the breeding season, and it may be that like those animals, the salmon returns to sea lank and lean, and comes from it in good condition. It is evident that at times their food is both fish and worms, for the angler uses both with good success, as well as a large gaudy fly, which the fish probably mistakes for a gay libellula, or dragon fly" ("Gen. Zool." v. Part I., p. 42). The preposterous idea that any fish can subsist without ever taking food was maintained by Daniel, who stoutly argued that the salmon lived on nothing but water! Dr. Knox states that from the time the salmon enters the fresh water it ceases to feed, properly speaking, although it may occasionally rise to a fly, or be tempted to attack a worm or a minnow, in accordance seemingly with its original habits as a smolt. But after first descending to the ocean and tasting its marine food, it never again resorts to its infantile food as a constant mode of nourishment. This great fact, he continues, well understood by fishermen and anglers, has been placed by Mr. Young, of Invershaw, beyond all doubt. Nothing is ever found in the stomach and intestines of the fresh sea salmon but a little reddish substance, which Dr. Knox, after a careful microscopic examination, concluded to be the ova of some species of Echinodermata. Of the salmon, therefore, while in the sea, he maintains this to be the sole and constant food.

M. Valenciennes describes the salmon as voracious, and states that its food consists of fishes (Ammodytes Tobianus), but Dr. Knox asserts that there exists not a single fact in the history of British salmon to support this opinion. He refers to various fanciful theories suggested by fishermen and others in regard to the marine food of the salmon, and concludes by stating that in spring, as the spawn fish are descending with the smolts, they may occasionally be tempted with an artificial fly or lob-worm, but as to their feeding regularly in rivers, Mr. Young's experiments have negatived the assumption beyond all doubt.

Dr. Knox is here partly right and partly wrong; he is right in saying that the fresh-water salmon seldom or ever feeds, but unquestionably wrong in maintaining so positively that other fish never constitute the salmon's food in the sea. The same writer thought that the excellent quality of the salmon as an article of food is to be traced to the rich eggs of the Echinodermata, which he considered to be its principal food.