however, utterly improbable, it may easily be calculated that for every meteor grazing our atmosphere (at a height not exceeding 70 miles), twenty-eight travel directly towards the earth's surface. But the proportion must in reality be very much greater, since our supposition implies the possibility of a meteor travelling through the air in a direction actually tangent to the earth's surface, or passing through about 1,450 miles of air, including the densest strata. Since meteors seldom penetrate to a vertical depth of more than twenty or thirty miles, without dissolution, it is very unlikely that meteors travelling parallel to the horizon should penetrate to a vertical depth even of ten or fifteen miles-since, to do so, their actual path through the air would be many times longer. Assuming that meteors could escape after penetrating in this manner to a depth of twenty miles, we should have, for every meteor so escaping, almost exactly one hundred whose substance, whole or dissolved, would reach the earth. Even escaping meteors would never again appear as members of the November shower, since their orbit, after grazing contact of the kind supposed, would be very different (owing chiefly to their loss of velocity) from that they originally pursued.

In the fact that such multitudes of meteors have, during so many and such brilliant displays of November showers as have been recorded, been stolen by the earth from the stream to which they belonged, serves to afford some conception of the immense number of meteors forming the November stream. Yet clearer views will be formed on this point if we consider the evidence we have respecting the length, breadth, and thickness of the cluster, during the passage through which the display is visible. I have not space to dwell here on Adams' investigation of the meteoric orbit. But it is necessary to point out that we must now greatly increase our estimate of the length of the cluster causing the November showers. The recurrence of displays during two or three consecutive years was simply accounted for on the theory of a nearly circular orbit, without assuming for the cluster a length of more than a few millions of miles. Now that we know that the meteorflight travels in an orbit of great eccentricity, and with a period of 33 years, we know that the portion passed through by the earth in one year is several hundreds of millions of miles away, when the earth next passes through the meteor orbit. Hence the recurrence of displays leads us to estimate the length of the cluster by hundreds of millions of miles, instead of by mere millions.

Next, for the breadth of the stream. On this point we have no exact information. It is sometimes assumed that the fact that the display may be seen in one hemisphere, while in

another it is not seen (as last year, for instance, in America), points to a limit of breadth. But this is not the case. If we consider Figs. 1 and 2 we shall see that America was on the sheltered side of the earth during the whole time of the display. When America had come to the side turned towards the radiant, the earth's globe had, in all probability, passed through the meteor-stream. So that the limits of the thickness, and not of the breadth of the stream, were indicated by the non-visibility of the meteors in America. Before the display had begun in England, the meteors, were seen from Kishnagur, fifty miles north of Calcutta, and they continued visible until the time of sunrise there. This would assign a breadth of not less than 4,000 miles to the stream. But as, throughout the continuance of the display, the earth was crossing the breadth of the stream at the rate of about 1,000 miles an hour, we can assert positively that the breadth of the stream exceeded 6,000 miles. In reality, however, a very much greater breadth may be assigned, with great probability, to the meteor-stream. For if we consider the nature of the stream and the manner in which it has been probably generated in the track of Comet I., 1866, we shall see the great probability that its breadth exceeds its thickness. For the causes tending to make meteors leave the mean plane of motion, are much less efficient than those tending to distribute the meteors over that plane. Now the earth, during the time of the display, was crossing the thickness of the meteor-stream at the rate of about 18,000 miles an hour. Therefore, since the display lasted at least six hours (counting from the time of its being observed in India, when England was, as yet, on the earth's sheltered side), we cannot assign to the stream a less thickness than 100,000 miles. The breadth is probably at least ten times as great.

It may be assumed as certain, that it is the passage of the earth through the thickness of the meteor-stream which limits the duration of the display.

I shall conclude by quoting two observations, showing that the fine powder in which meteors reach the earth may be detected. Dr. Reichenbach collected dust from the top of a high mountain, which had never been touched by spade or pickaxe; and on analysis he found this dust to consist of almost identically the same elements as those of which meteoric-stones are composed-nickel, cobalt, iron, and phosphorus. Again, Dr. Phipson notes, that "when a glass, covered with pure glycerine, is exposed to a strong wind, late in November, it receives a certain number of black angular particles," which "can be dissolved in strong hydrochloric acid, and produce yellow chloride of iron upon the glass-plate." I quote these

observations on account of the interest attaching to them; not as evidence to show that the majority of shooting stars never pass out of the carth's atmosphere. Such evidence is not

required-the fact being mathematically demonstrable.

THE LARGEST BLOOD DISCS KNOWN-SINGULAR CAPTURE OF A CANADIAN REPTILE, MENOBRANCHUS LATERALIS.

A WEEK or two since we received by post from Canada two glass slides containing numerous blood discs of large size, which at once reminded us of those of the Lepidosiren, but on comparison were found much bigger. A few days later came the following interesting letter from a Canadian subscriber, who has not favoured us with his name, but to whom we beg to express our thanks. The Menobranchus of which he speaks belongs to an interesting group, the Ampibia, possessing permanent gills, and comprehending the Proteus, Siren, etc.

The letter runs as follows:

"I take the liberty of sending you two slips of glass, upon which you will find specimens of the blood discs of Menobranchus lateralis, one of the salamander family, inhabiting Lake

1

2

BLOOD DISCs.-1. Menobranchus lateralis. 2. Siren. 3. Man. × 300. Ontario. It is remarkable for being furnished with both lungs and gills, so as to be able to live either on land or in the water. It is seen occasionally ashore, but usually prefers the water. It much resembles a similar animal found in the Lake of Mexico (Axolotlus pisciformis), but differs from that species in the number of its toes, of which it has four on each foot, and in having no toe-nails. There is a good likeness of this reptile in the "Encyclopædia Britannica," vol. xix., 8th edition; but it is in reality considerably darker than the picture. They are not often seen here. I have known only five or six taken alive in thirty years. The specimen of which I send you the blood discs was taken by a water-snake, which brought it

ashore, and had it half swallowed, when in his turn the snake was captured by a spectator. When I saw them the snake (about four feet long) had disgorged his prey, which was covered with blood and dust, and apparently dead. On being placed in a vessel of water, the lizard immediately revived, and then appeared to be furnished with three branchial tufts on each side of his head, which were dusky on the upper side, but the fine filaments with which they were thickly tufted were of a dark red colour. They pulsated with a vigorous stroke about fifty times each minute, but would occasionally cease awhile when the animal was disturbed. Every minute or two he raised his head above the water, and opening a pretty wide mouth, took a gulp of air, which he afterwards expelled from the gills when under water. He was about thirteen and a half inches long and two broad, and was the largest I have seen of this kind.

"The morning after his capture it became apparent that the wounds inflicted by the snake would soon cause his death. The branchial motion had wholly ceased, and the reptile made a respiration of air only occasionally. When he appeared dead I made a small opening in his breast, and got some of his blood, which I hope that you will be pleased to have an opportunity of examining. The blood discs are of a very great size, so as to be visible to the naked eye. I have a slide of the discs of the Siren mounted by Topping, and sent to me as the largest known. They are not, however, half the size of those which I send you, measuring on the long diameter, and on the short diameter nearly as much, while the discs of the Menobranchus measure, and the respective areas are in the proportion of 12 to 25. These measurements refer to the largest discs; those of a medium size measure × 75. "The Siren is not a native of Canada, but of South Carolina, twelve degrees of latitude south of this place.

"CANADA, 26th August, 1867."

"A CANADIAN SUBSCRIBER.

MAN AND THE PLEISTOCENE MAMMALS OF GREAT BRITAIN.*

(Read at the Congrès Paléoethnologique.)

BY W. BOYD DAWKINS, M.A., F.R.S., MEMB. CORRESP.

THE remains of man have been found in various parts of Great Britain, associated with the remains of many of the postglacial group of mammals, both in bone caverns and in river deposits. The implements found in the latter are precisely of the same character as those from the banks of the Somme, while, on the other hand, those in the caverns are smaller, and approach nearer to those found in the cave of Moustier than to any others. We will first examine the mammals proved to have coexisted with man during the time that ancient gravel and loam beds were being swept down by rivers that now flow at a lower level.

So far back as the year 1715,† a spear-head of flint was discovered, along with the remains of a mammoth, in the gravel of the Thames, near Gray's Inn Lane, in London, and is preserved in the British Museum. No particular notice was taken of this discovery until the year 1860. At the end of the last century, implements of a similar kind were found at Hoxne, in Suffolk, and from that time down to the present numerous traces of man have been found in the same layer, along with the remains of mammoth, deer, and horse. Until, however, the discoveries of M. Boucher de Perthes called the attention of English savants to the existence of man in the post-glacial epoch, no notice was taken of the earliest known implements that man left behind him in the gravel. In the year 1861,§ Mr. Wyatt found, along with the remains of man, in the gravels of Bedford, the cave bear, bison, stag, reindeer, Elephas antiquus, hippopotamus major, and tichorhine rhinoceros. Among the fluviatile shells was a fresh-water mussel, extinct now in Britain, Unio Batavus, but which still lives in the Oise. The remains found by Dr. Blackmore at Salisbury, and described by Mr. Evans in his paper on flint implements in 1864,|| were not derived from the same bed as the implements, but from one of a different character occurring at a lower level. They cannot, therefore, be cited as proving the coexistence of man with the extinct mammalia in Wiltshire.

The French title of this paper was, "Sur les Mammifères Pleistocènes Trouvés avec L'Homme dans la Grande-Bretagne." "Archeologia," 1800. § "Quart. Geol. Journ.," vols. xix. xx. || Quart. Geol. Journ.," vol. xx.

+ "Archæologia," 1860-2.