a coating of clay. The transposed pieces of bark united to the stems to which they were applied; and in the autumn it apeared evident that a layer of alburnum had been formed beneath the transposed pieces of bark which were then taken off.

The original sinuosities of one of the pieces of bark (that of the crab tree) were not discoverable but the une ven surface of the stem from, which it had been taken, though covered with a smooth bark, remained unchanged. The newly generated alburnum, beneath the transposed bark, appeared perfectly similar to that of other parts of the stock, and the direction of the fibres, and vessels did not in any degree correspond with those of the transposed bark.

Repeating this experiment,' says Mr. Knight,' I scraped off the external surface of the alburnum in several spaces, about three lines in diameter, and in these spaces no union took place between the transposed bark and the alburnum of the stock, nor was there any alburnum deposited in the abraded spaces; but the newly generated cortical and alburnous layers took a circular and rather ellip tical course round these spaces, and appeared to have been generated by a descending fluid, which had divided into two currents when it came into contact with the spaces from which the surface had been scraped off, and to have united again immediately beneath them.'

It is allowed, however, by Mr. Knight himself that these experiments are not decisive, since under the transposed bark, a new cortical, substance is formed, and if there be any transmutation, of course it must be of this new substance, and not of the transposed bark. But the mode of production of the alburnum opposes the hy pothesis; the commencement of alburnous layers in the oak is distinguished by a circular row of very large tubes which are produced in spring, they pass through a soft gelatinous substance, much less tenacious than the bark itself. Nor is it ever observed that the bark is converted into this soft gelatinous substance. These tubes are generated within the interior substance of the bark itself, which is well defined, and during their formation, the vessels of the bark are distinctly visible, as different organs.

Among observations supposed to favour the hypothe sis which Mr. Knight controverts, one of Duhamel's deserves notice. When the bud of a peach tree, with a piece of bark attached to it is inserted in a plain stock, a

layer of wood perfectly similar to that of the peach-tree will be found in the succeeding winter, beneath the inserted bark. The fact is admitted, whilst it is justly remarked that it is impossible to conceive that a piece of bark can be converted into a layer of alburnum of twice its own thickness, without any perceptible diminution of its substance. The bud is a well organized plant. Mr. Knight observed when he destroyed the buds, in the succeeding winter, and left the bark to them uninjured, this species of albarnum was no longer produced.

The bark nevertheless continued to live, though perfectly inactive, till it became covered by the successive alburnous layers of the stock; and it was found many years after inclosed in the wood. It was, however still bark, though dry and lifeless, and did not appear to have made any progress towards conversion into wood.'

VII. Some Account of Cretinism. By Henry Reeve, M. D. of Norwich. Communicated by William Hyde Wollaston, M.D. Sec. R.S.-Cretins are the miserable idiots so frequently met with in Switzerland and other Alpine countries, in which the disease is endemial. It is often accompanied with goitres, (bronchocele) but this is not a tendant.

constant at

His head. Dr. R. remarks, is deformed, his stature diminutive, his complexion sickly, his countenance vacant and destitute of meaning, his lips and eye-lids coarse and prominent, his skin wrinkled and pendulous,his muscles loose and flabby. The qualities of his mind correspond with the deranged state of his body which it inhabits; and cretinism prevails in all the intermediate degrees, from excessive stupidity to complete fatuity."

Dr. Reeve adopts M. Saussure's account of the causes of this disease, which he thinks sufficient to account for the phenomena.

'The vallies,' he says, where cretinism is most frequent, are surrounded by very high mountains; they are sheltered from the currents of air, and exposed to the direct, and still more to the reflected rays of the sun. The effluvia from the marshes are very strong, and the atmosphere humid, close, and oppres sed. All the cretins that I saw, were in adjoining houses, in the little village called La Batia, situated in a narrow corner of the valley, the houses being built under ledges of the rocks, and all of them very filthy, very close, very hot, and miserable habitations. In villages situated higher up the mountains, no Cretins are to be seen, and the mother of one of the children told me of her own accord, without my asking the question, that

her child was quite a different being, when he went up the mountains, as she called it, for a few days.'

This is certainly a very strong fact, and perhaps as convincing a proof of the ill effects of a polluted atmosphere as can be adduced. Whether it be the sole cause we doubt, as we believe that much of the difficulty in the investigation of the remote causes of disease, has arisen from not considering them as complicated, and attributing too much to one. Dr. Reeve adjudges the water to be harmless; several faels, however, make us suspect the reverse, nor do we think it enough to say, that the water used is free from calcareous matter, and well tasted. Whatever be the causes of this disease, they very soon show their activity, they begin to operate soon after, perhaps even before birth.

Dissections show how much this malady affects every part of the system. Dr. Reeve has given two plates of the skull of a cretin of thirty years old, in which the suture is not closed, the second set of teeth are not out of their sockets, and none of the bones are distinctly and completely formed. He observes,

There is no fact in the natural history of man, that affords an argument so direct and so impressive, in proof of the influence of physical causes on the mind, as cretinism. It shows, moreover, that the growth of every part is essentially connected with the conditions in which it is fit to exercise its peculiar functions; and it fares in this respect with the intellectual as with the bodily powers.'

In the justness of both of these remarks, we heartily coincide; and wish that the former, in particular, were much more deeply impressed on the minds of pathologists. Till it is so, we are persuaded that the condition of mankind will be stationary at least. It is well if it be not retrograde.

VIII. On a new Property of the Tangents of the three Angles of a plane Triangle. By Mr. William Garrard, QuarterMaster of Instruction at the Royal Naval Asylum at Greenwich. Communicated by the Astronomer Royal.

IX. On a new Property of the Tangents of three Arches trisecting the circumference of a circle. By Nevil Maskelyne, D.D. F. R. S. and Astronomer Royal.-The property is that the squares of the radius, multiplied into the sum of the three tangents of the three arches equal the products of the tangents.

To demonstrate this property, let A B C'be the three arches; t, u, w, the respective tangents, r the radius the whole circumference." Then A+B+C÷✪ and ́C=0·

tang.C=tang.(−A+B=-tang.A+B'(the tangent of any arch and of supplement to the whole circumference,being equal and contrary to one another, or the one negative of the other). "Therefore t, A + t, B+t, Cort+u+w=t+ u

; but t and u are the expressions

for the tangents of A and B respectively, and

is the expression for the tangent of C or for w.

Therefore

2

r2 × t + u+w or the square of a radius multiplied into the sum of the three tangents of A, B, and C tuw, = product of the tangents." Q. E. D.

or the Mr. Garrard has, in the former of these papers, demonstrated the same property of the tangents of the three arches, of a semi-circle; that is to say, of the three angles of a plane triangle; but the demonstration being partly geometrical, we must refer our mathematical readers to the original.

-

X. An Account of the Application of the Gas, from Coal to Economical Purposes. By Mr. William Murdock, communicated by the Right Hon. Sir Joseph Banks, Bart. K.B. F.R.S. Mr. Murdock claims to be the first who has applied the gas from coal, to economical purposes. He first began to make experiments with this view, 16 or 17 years ago. In 1798, he constructed an apparatus for the manufactory of Messrs. Bolton and Watt, at the Soho foundry; and since 1802, the apparatus has been extended so as to give light to all the principal shops, where it is in regular use, to the exclusion of other artificial light. The observations contained in this account, were made at the cotton manufactory of Messrs. Philips and Lee, at Manchester, in the winter of 1807 and 8, where the light obtained by the combustion of gas, is used upon a very large scale.

The total quantity of light used during the hours of burning, has been ascertained, by a comparison of shadows, to be about equal to the light which 2500 mould candles, of six in the pound, would give. The gas is distilled in large iron retorts, from which it passes in iron pipes, into large reservoirs, or gazometers, where it is washed and puCRIT. REV. Vol. 16. January, 1809.

D

1

rified, previous to its being conveyed through other pipes, called mains, to the mill. These branch off into a variety of ramifications, (forming a total length of several miles) gradually diminishing in size. The burners, where the gas is consumed, are connected with the mains, by short tubes, each of which is furnished with a cock, to regulate the admission of gas to each burner, and to shut it totally off when requisite. The burners are of two kinds the one is upon the principle of the Argand lamp, the other is a small curved tube with a conical end, with three little perforations. The whole number employed, amounts to 271 Argands, and 633 curved tubes. The whole of the burners require an hourly supply of 1250 cubic feet of the gas produced from cannel coal. The superior quality and quantity of the gas produced from that material, having given it a decided preference in this situation over every other coal, notwithstanding its higher price. The following is the economical statement for one year :

Cost of 110 tons of cannel coal
Ditto of 40 tons of common ditto

£.125

20

145

93

Deduct the value of 70 tons of coak

The annual expenditure in coal, after deducting the value
of the coak, and without allowing any thing for the tar,
is therefore

And the interest of capital, and wear and tear of appa

ratus

52

550

making the total expence of the gas apparatus, about 6001. per

annum.

That of candles, to give the same light, would be about 20001. For each candle, consuming at the rate of 4-10ths of an ounce of tallow per hour, the 2500 candles, burning upon an average of the year, two hours per day, would, at one shilling per pound, the present price, amount to nearly the sum of money abovementioned.'

If the comparison were made upon an average of three hours per day, (which, in some factories, is a just average) the advantage of employing the gas light, would be still greater, for the interest of the capital, and wear and tear of the apparatus, would be nearly the same, But we should have been pleased to see not a theoretical saving, from a calculation of the light afforded, but an actual saving, from a comparison of the real expenditure of the proprietors in candles, before the adoption of the gas lights. These lights may afford a greater illumination than is absolutely neces