this part of the subject, but to state to you a recent instance of one of those animals being found in a very singular situation. I was not an eye-witness; but the person who has charge of my father's woods here, a man for whose integrity I can be answerable, told me the particulars.

A quantity of timber being felled here, a wright, who had made some purchases, came to take his trees away, and amongst the rest a beech, which had grown with a smooth, straight, unbranched, stem of about 30 feet high, above which it divided into two large limbs. As this tree was lying on the ground, the wright and his man set about cross cutting it with a saw just below the cleft, when, to their surprise, the stem was no sooner divided than a large toad crept out of a circular hole, the upper and smaller part of which had been cut off by the saw. As far as I can make out from conversation with the man above alluded to, the tree had all the appearance of being quite solid above; yet I have no doubt that some slight, though perhaps almost imperceptible, communication, must have existed from the fork into the hole where the toad was lodged; and I am the more satisfied of this from the account which the man gives of the appearance of the interior of the hole, which seemed to be sheathed all round with something resembling bark.

But the curious query arising from this fact is, how came a toad to be lodged so high? The toad has no power of crawling perpendicularly so as to have ascended the smooth bark of a straight tree to such a height. I know from my own observations that trees grow in altitude in two ways: 1st, Something is annually added to the height of the tree by the new shoots: and 2dly, in addition to this mode of increment, the whole tree seems to stretch itself yearly out of the ground, throughout its entire length, to a very considerable extent, as I have proved by measuring the height of knots upon trees at different periods. But with all this I do not think it very rational to suppose that the cleft in question, which may have once extended quite down to the hole, could have ever existed so near the ground of a size sufficient to have admitted of a toad crawling into it. The only way in which it appears to me that this circumstance can be accounted for, is by supposing that the spawn, after being removed from the female by the obstetrical aid of the male toad, must have been transported and dropt into the cleft of the tree by some bird.

As to what Pennant and others say of the obstetrical aid afforded by the male to the female toad, I am led to suspect that the object of the operation is more for the purpose of impregnating the spawn as it is dragged from the female than any thing else. It appears to be the same with frogs. In the course of a solitary walk in the beginning of last March, my attention was excited by an uncommon commotion in a shallow pool of water not much more than four feet square. My approach to ascertain the cause being rather too hasty, I had only time to observe it was occasioned by a parcel of frogs, when immediately on my advance they disappeared under

water, concealing themselves beneath a quantity of spawn already floating on the surface. Having placed myself behind an adjoining hedge, through which I could perfectly see the pool, being about two yards from its surface, and at the same time without giving any disturbance to its inhabitants, I remained quiet for more than a quarter of an hour. At length, when my patience was nearly exhausted, I saw the head of a frog rise above water; and on a closer inspection I perceived underneath the head of another one, which seemed to be embraced by the first. In this way they silently raised themselves pair by pair, till there were not less than 50 or 60 pairs of them in the small space I have already mentioned. In a short time the little pool was all in action. Those frogs which were mounted on the backs of the others seemed to be busily employed with their hinder feet and legs, whilst the fore legs of each firmly embraced the body of his mate. In some too a mass of spawn seemed to move after the pair as they altered their position in the pool. These violent exertions of what I took to be the males continued without any intermission, and with so much force as very considerably to agitate the little pool for some time, until the noise of a person passing on horseback alarmed them, and they were all again under water in a moment. From the hinder parts of what I took to be the female frogs having been so much under water, I could not positively assert the fact, but I had not a doubt, from the nature of the motions I saw, that the animals were engaged in an operation similar to that which is ascribed to the toad; and I was confirmed in this belief by observing on my return, five or six hours afterwards, that the quantity of spawn had been nearly doubled; and though I approached the pool with the utmost caution, I could not see a single frog, and had every reason to think, from a careful examination of the shallow pool, that they were all gone.

I fear the above may be very uninteresting to you; and if so, I have to apologize for troubling you with it.

I have the honour to be, Sir,

Fountain Hall, by Tranent,

Your obedient humble servant,
THOS. LAUDER DICK.

May 8, 1815.

ARTICLE III.

On the Red Sand-stone Formation. By Professor Jameson.

THIS important formation has been met with in the most widely distant parts of the globe, and generally occupying great tracts of country. It rests sometimes on primitive rocks, but more frequently on those of the transition class; and in many countries it is covered

with an extensive series of newer rocks. It is distinctly stratified; and the strata vary from the horizontal to the nearly perpendicular position. The strata are sometimes waved, sometimes disposed in a concentric lamellar manner, but are more frequently straight. Sometimes vertical strata are to be seen meeting others which are in a horizontal position, and occasionally vertical strata are contained in masses of nearly horizontal or slightly inclined strata. Occasionally the strata in a small district appear disposed in every possible posi tion; and at first sight suggest to us the idea either of great original inequalities, or of violent action on the strata after their formation, but which, upon more careful examination and consideration, would seem rather to intimate that the whole mass of strata is composed of a series of distinct concretions, in each of which the layers or strata vary more or less in position.

Red sand-stone contains many different rocks, either in beds, mountain-masses, or veins. The following are the principal kinds of rock I have met with in the red sand-stone of Scotland.

1. Red-coloured Slate-clay.-This rock occurs in beds that vary in thickness from a few inches to several fathoms. It is sometimes so highly impregnated with calcareous earth as to pass into marl. Its red colour is sometimes variegated with stripes, layers, and circular portions of a green colour. It passes sometimes into claystone, and sometimes into clay-iron-stone. It occurs in Salisbury Craigs, near Edinburgh; Pentland and Ochre Hills; Isle of Arran; Ayrshire, near Saltcoats; Drumfrieshire; Angus-shire, &c.

2. Clay-stone. This mineral occurs in beds that vary in thickness from an inch to several yards. It alternates with the preceding rock, and also with red sand-stone, and some other rocks subordinate to it. It occurs in Salisbury Craigs, Pentland and Ochil Hills, Arran, Ayrshire, Dumfrieshire, Angus-shire, &c.

3. Clay-iron-stone.-It occurs in layers, or in irregular shaped masses, generally included in slate-clay. It is a frequent mineral in many red sand-stone districts, as in the Island of Arran, Dum frieshire, Lothians, Angus-shire, &c.

4. Trap Tuff. This singular and interesting rock occurs in the red-sand-stone in beds, which are frequently of great thickness. It passes into clay-stone and red sand-stone. It is by no means an uncommon rock in several of the red sand-stone districts of this country, as in the Lothians, Arran, Angus-shire, &c.

5. Amygdaloid. This rock, like the trap tuff, occurs in great beds or hills connected with the red sand-stone, and occasionally imbedded cotemporaneous masses of it are met with in the sandstone. It passes into the tuff and sand-stone. It is one of the rocks of the red sand-stone districts in East Lothian and Mid-Lothian, Islands of Bute and Arran, Angus-shire, &c.

6. Basalt. This rock occurs in beds and veins in the red sandstone of Bute, Arran, Ochils, Pentlands, Lothian, Angus-shire, &c. 7. Clink-stone. This beautiful rock is abundant in several red

sand-stone districts in Scotland, in beds, hills, and veins. The following are a few of the localities of this rock: Arran, East Lothian, Ochils, Pentlands, Angus-shire, &c.

8. Green-stone. Beds, imbedded cotemporaneous masses, mountain masses, hills, and veins, of this rock occur in the red sand-stone formation of Scotland. Thus it is met with in East and Mid Lothian, Ochil Hills, Arran, Bute, Renfrewshire, Ayrshire, Angus-shire, &c.

9. Pitch-stone.-Green and black coloured varieties of this rock are met with in the form of imbedded masses, beds, and veins, in the red sand-stone of the Island of Arran.

10. Felspar.-Beds of compact felspar, often passing into claystone, occur in the red sand-stone of Arran, Pentland Hills, Ochil Hills, &c.

11. Porphyry. -Varieties of this rock, namely, clay-stone, horn-stone, and felspar-porphyry, occur in beds, hills, and veins, in the red sand-stone formation. The Pentland and Ochil Hills, the Island of Arran, the upper ward of Lanarkshire, Angus-shire, afford examples of porphyry in red sand-stone.

12. Lime-stone and Lime-stone Conglomerate. These rocks occur in beds in the red sand-stone of East and Mid Lothian, in that of the Ochil and Pentland Hills, of Arran, Dumfrieshire, Ayrshire, Lanarkshire, Renfrewshire, Angus-shire, &c.

13. Coal. Of this mineral several kinds occur in the red sandstone, viz. glance-coal, slate-coal, and pitch-coal; and they are met with in Arran, Dumfrieshire, Lothian, &c.

From the short enumeration just given, it is evident that the red sand-stone formation is much more interesting than has been generally imagined. The great variety and abundance of trap, pitchstone, and porphyry rocks, contained in it, their transitions into each other and into the sand-stone and clay are very striking facts in their natural history, and deserving the particular attention of those who take an interest in the volcanic and neptunian theories of their formation. Those naturalists who are inclined to think favourably of the opinion which maintains the chemical formation of sandstone will adduce the various kinds of structure exhibited by the red sand-stone as so many facts illustrative of its plausibility; and the miner and engineer, if they adopt this opinion, will probably obtain an easy solution of many difficulties that occur in their respective arts, and practical rules of value and importance to them.

ARTICLE IV.

On the Method of Illuminating the Streets by Coal Gas. By Mr. Frederick Accum.

YOUR Correspondent in the Annals of Philosophy for April, p. 313, who appears to be alarmed concerning the safety of the application of the gas light illumination, and is desirous of obtaining information concerning certain facts relating to the scheme of procuring light by means of carbureted hydrogen, or coal gas, is hereby informed that the explosion he alludes to was occasioned in consequence of a quantity of coal gas having been suffered to enter into the building where the gazometer was erected, and where it mingled with common air, and was set on fire by the approach of a lighted candle. I give this statement from a letter before me, written by the proprietors of the establishment at which the accident happened to a Gentleman in this town. They who are familiar with the system of lighting with coal gas will readily allow that gas light illumination is more safe than the illumination by candles or lamps. As a proof of this statement, it need only be mentioned that the fire-offices engage themselves to ensure cotton-mills and other public works at a less premium where gas lights are used than in the cases of any other lights. In fact no danger can arise from the application of gas lights, in any way but what is common to candles and lamps of all kinds, and is the fault of none of them. Even in this case the gas lights are less hazardous. There is no risk of those accidents which often happen from the guttering or burning down of candles on carelessly snuffing them. The gas light lamps and burners must necessarily be fixed to one place, and cannot fall, or otherwise become deranged, without being immediately extinguished. Besides, the gas lights emit no sparks, nor are any embers detached from them. And with regard to the production of the gas, it is certain that the manufacture of coal gas is a process perfectly safe. There is no more risk in the action of a gas light machine properly constructed than in the action of a steam engine built on just principles. No part of the machinery is liable to be out of order. There are no cocks to be turned; no valves to be regulated; nor can the operator derange the apparatus but by the most violent efforts; and when the stock of gas is prepared we may depend as much on its lighting power as we depend on the light of a certain number of candles or lamps. To obtain this gas the workman is not called upon to exercise his own judgment: it requires nothing more than what the most ignorant person, with a common degree of care and attention, is competent to perform.