pro

9. The law of variability which expresses the ratio of the ducts of the flow to the degrees of temperature is manifested with so much the greater regularity the smaller the diameter of the tube is in which the experiments are made.

10. The temperature which exercises so great an influence on the products of uniform flow ceases to have a sensible influence when the motion takes place in open canals, or in ordinary tubes whose diameter is too great to be capillary.

The author passes to the application of his experiments to the determination of the ratio of the temperature, and the thickness of the coat of fluid adhering to the sides of the tube.

The superficies of the transverse section of the tube is diminished by a circular crown, the thickness of which varies with the temperature of the fluid. He expresses the surface of this crown by a series of this form :

S=A+BT+ CT2 + DT3+ &c. T being the temperature. He seeks the value of the coefficients from experiment, either confining himself to T2, or in proceeding as far as T3. He deduces from this the formula of the thickness e: and by means of these two formulas he calculates the whole of the experiments made with different series of tubes, which enables him to compare these formulas with each other, and with the quantity of water which really flows out. The result of these comparisons for the first series of tubes is, that the product calculated by the formula, employing the first three powers, is greater than the product observed; and that when the third power is suppressed, and we confine ourselves to the first two, the calculated product is a little too small. But all these differences are extremely slight. From experiments made with the second series of tubes, it results that we may neglect the third power, so that the curve is only of the second degree.

These conclusions may be verified by the simple inspection of the tables, which exhibit all the circumstances of each experiment.

The author then discusses the different causes of the errors which could influence the results, and produce the slight differences remarked in them.

He thinks that we may always assign the ratio which exists between the diameter of a capillary tube, its size, and the depression of its lower orifice below the surface of the fluid in the reservoir from which it flows, and between the temperature and the flow per second when the motion has become linear.

He makes similar calculations for the thickness e of the coating for the same two series, and in the double hypothesis of the equation of the second degree and that of the third. He determines this thickness for every five degrees of the thermometer from the freezing to the boiling point. The results of these new calculations are likewise exhibited in two tables, where we remark easily that the thickness of the fluid coats which cover the inner surface of the tubes is less in the small tube than in the large. Hence the author concludes that these thicknesses do not depend solely upon the temperature, but likewise upon the radius of curvature, and the

transverse section of the tube, which would not be the case if the action of the tube did not extend to a finite distance from the surface. This remark will occasion new researches, which will be the subject of another memoir.

(To be continued.)

ARTICLE X.

SCIENTIFIC INTELLIGENCE; AND NOTICES OF SUBJECTS
CONNECTED WITH SCIENCE.

I. Arragonite.

It has been long known to mineralogists that the crystalline forms of calcareous spar and arragonite are different; and Haüy demonstrated that no admissible decrements could reconcile their primitive forms. In the year 1813 Stromeyer announced that he had discovered in the arragonite of France 4 per cent. of carbonate of strontian; and in the arragonite of Spain, 21 per cent. of the same salt. He stated, at the same time, that he considered the crystalline shape of arragonite as the same with that of carbonate of strontian. It has been known for some years that certain substances, when they amount only to a small proportion of a compound, impress upon the whole, notwithstanding their own crystalline form. Thus two or three per cent. of sulphate of iron is capable of inducing its own form upon sulphate of zinc. White cobalt ore owes its cubic form to a small portion of iron pyrites which it contains. Gres de Fontainbleau has the crystalline form of calcareous spar, of which it contains only a small portion. Stromeyer conceived that in like manner the small proportion of carbonate of strontian in arragonite influenced the crystalline form. A short time before his death, Gehlen announced that he had met with very well-defined crystals of carbonate of strontian, and that the form was precisely the same as that of arragonite. This question has been lately discussed at great length by Professor Fuchs, of Landshut. The result of his examination is, that the crystals of carbonate of strontian have a considerable resemblance to those of arragonite, but that they are by no means the same (Schweigger's Journal, xix. 113). The crystals of carbonate of strontian found lately near Saltzburg are regular six-sided prisms. Those of arragonite are likewise sixsided prisms, but not regular; for four of the angles are of 116°, and the two others of 128°. Now M. Haüy has demonstrated that the primitive form of arragonite cannot pass into the regular hexahedron in virtue of any admissible law of decrement. Besides this, Bucholz and Meisner analyzed different specimens of arragonite, which were destitute of carbonate of strontian; and Laugier found onlyth part of this salt in the arragonite of Bastenes. From these facts we may consider it as demonstrated that the opinion of Stromeyer is inaccurate. It follows, therefore, that the cause of

the discordance between the crystals of arragonite and calcareous spar is as problematical as evér.

II. Barley.

According to Proust, the constituents of barley-meal are as follows: Yellow resin

Gummy and saccharine extract.

Gluten

Starch

Hordein

1

9

3

32

55

100

The resin is obtained by digesting the meal in alcohol. It is a pitchy substance, which seems to me better entitled to the name of oil than of resin. I examined it many years ago, and was much struck with its flavour, which is precisely similar to that of spirits made from unfermented barley. Hence I was disposed to consider that flavour as owing to the presence of this oily substance.

The gummy and saccharine matter are obtained by digesting the barley-meal in cold water. The gluten precipitates in flocks when this aqueous infusion is heated.

The starch and hordein constitute the powder that remains after the preceding processes. By boiling this powder in water, the starch is taken up, while the hordein remains. The substance to which Proust has given the name of hordein has much the appearance of the sawings of wood, and possesses, according to him, the properties of lignin; or at least it approaches very closely to that vegetable principle in its properties.

III. Malt.

According to Proust, the constituents of malted barley are as follows:

Resin
Gum

....

1

15

15

1

56

12

100

He affirms that barley in malting loses a third of its weight (Ann. de Chim. et Phys. v. 342); but I can assure the reader that the whole of his account of malt and malting is very far from accurate. The average loss in more than 50 malting processes on a pretty large scale, which I myself superintended, and during which much care was taken to ensure accuracy, was only 20 per cent. The malt in these cases was weighed just when taken off the kiln, and the barley had been weighed just before it was put into the steep. I found that if the barley was kiln-dried, it lost 12 per cent. of its weight; and that the malt, when kept for some time in a granary, recovered the same proportion of weight. Hence I conceive it follows that the true loss of weight in malting does not exceed

eight per cent., or rather less than th. One half of this loss is to be ascribed to matter dissolved from the husk of the grain by the steep-water, and to grains of barley bruised and destroyed by the malster while turning the malt upon the floor; so that the real loss in malting does not, I believe, exceed four per cent. I leave it to M. Proust to decide whether it is likely that so very remarkable a change should be produced in the composition of barley-meal by malting, and yet so small a change in the weight. The hordein of Proust I consider as starch in a particular state, somewhat similar to the fibrous matter of potatoes. The malting partly converts it into the state of sugar, and partly into that of common starch, by destroying a certain unknown glutinous substance which glues the particles of it so firmly together.

IV. Brewing.

M. Proust's notions of brewing by means of barley and malt are obviously very imperfect. He says the great product of the fermentation is carbonic acid. The fact is, as I have determined by numerous experiments upon a large scale, that the portion of malt which is dissolved is resolved by fermentation into nearly equal weights of carbonic acid and alcohol of the specific gravity 0-825. When raw grain is employed by the distillers, it undergoes, while in the mash tun, a change similar to that induced on barley by malting; for the wort is just as sweet-tasted as the wort from malt. V. Effect of Lightning on a Tree.

SIR,

(To Dr. Thomson.)

George-street, Edinburgh, July 23, 1817. In my walk two days ago I happened accidentally to step into Craiglockart Garden, near the village of Slateford, about two miles west of Edinburgh, where, after inspecting the garden, hothouses, and romantic grounds, upon the wooded banks of the water of Leith, the keeper informed me that the thunder-storm of the 10th ult. had been particularly terrible at that spot, that the lightning had struck a tree on the side of the highway to the north of the garden wall, and had afterwards struck a man who had taken shelter in a neighbouring outhouse attached to the back of the garden, near the tree.

Wishing to ascertain the appearance of a tree struck with electric fluid (having often observed large blotches on the bark of trees said to have been caused by the lightning), I requested the keeper (Mr. Robertson) to show me the tree. I found it to be an English elm. The lightning had struck it at a small decayed knob about 15 feet above the ground, on the north side of the tree. It descended all round in a spiral form, and went off from the ground, destroying a large quantity of nettles and grass at the root of the tree in a southwest direction, towards the house where the man had taken shelter, where at the root of the tree I observed it had torn up the earth, which is still quite apparent, from the root of the tree, in the shape nearly of a large grooved wheel track, diminishing in size as it ex

tends outward. From this it entered the outhouse where the men were, and struck one of them so much that he was quite stupified for some time; and afterwards, as the men relate, the lightning went off by a skylight, although there is no visible mark of its course after quitting the root of the tree, and the grooved way, which does not extend above two feet from the tree, but is in the direction of the door of the house. In this house there was a considerable quantity of iron. Thus it would appear that leading a conductor to the earth is no certain rule of safety-the lightning does not descend into the ground.

The appearance of the effects of the fire upon the tree is quite different from the blotches which, in my ignorance, had frequently been passed upon me for the effects of lightning, and which probably is some disease of the tree, or animalculæ. The appearance of this tree is as if the top knobs of the outer cortex had been touched with a wright's plain, having a white glistening colour, as if after friction. No black traces remained upon the tree, and nothing bore the resemblance of burning, except some lateral branches, and the nettles and brushwood at the bottom of the tree.

The most surprising fact, however, is, that four years ago two trees (within a few yards of the elm that was struck) were in like manner successively struck with lightning. The one tree was a beech, and is now cut down, having decayed by the effects of the lightning: the other a fir, I believe, which remains a wretched spectacle to this day. This led me to inquire as to the contiguous metals imbedded in the ground under the spot.

Fortunately a well about 18 feet deep is sunk close by, which a man informed me he had been at the bottom of, and he assured me that the only mineral cut through in that depth was a greyish free

stone.

I have thought it proper to set down this information for you as I received it, and saw it. And if it can throw any light, or afford any hints to your learned friends, upon this most awful phenomenon of nature, I shall be happy. The shape of the groove by which the electric fluid escaped from the tree may perhaps be some foundation for ascertaining the form of the forked lightning. And from the direction as marked on the ground, and the circumstance of the man being so sensibly affected in the outhouse, it would appear to have been the same flash that did both.

I have the honour to be, Sir,

Your most obedient, humble servant,
JOHN GOVAN.

VI. Register of the Weather at New Malton, in Yorkshire.

July, 1817.-Mean pressure of barometer, 29.518; max. 29.83; min. 28-75. Range, 0.88 in. Spaces described by the curve, 5·00 in. Number of changes, 13.-Mean temperature, 58.92°; max. 70°; min. 48°. Range, 22°.-Amount of rain, 4:05 in. Wet days, 22, Prevailing winds, Westerly. N, 3. NE, 2. E, 1,