three visits to America he lost about thirty pounds in weight, which he recovered on returning home.

Another case has lately come painfully home to me. My son, acting as assistant to Major Herschel in his pendulum experiments, first at Kew, then at Greenwich and Portland Place, went on to Washington, and continued his duties there. His letters from this city were exuberant with enthusiasm and admiration of everything; but one of them was rather alarming, as it recorded the state of his own pulse, beating at 120 and upwards. Although a stubborn total abstainer, he was evidently in a state of abnormal excitement-a sort of dry-oxygen intoxication.

Presently, at New York, he became "dazed," and dangerous symptoms of incipient brain fever appeared, which being observed by Major Herschel, he was sent home at once. During his short absence he had grown thinner and taller, lank-jawed and sallow, displaying all the characteristic symptoms of what I cannot refrain from calling acute Americanitis, from which, by the natural operation of his native air and abundant sleep, he has recovered far more rapidly than was expected.

All that I can learn indicates that this is but an exaggerated typical case of what usually occurs to Englishmen, especially to growing youths, when they cross the Atlantic and proceed inland and southward.

I may mention another curious and illustrative case before proceeding to the intended application.

At one of those delightful Thursday evening meetings which were held at the house of the late George Combe, in Melville Street, Edinburgh, and named "circumtabular teas" by the facetious and brilliant Dr. Samuel Brown, some family portraits were shown and compared. These included photographs of the descendants of the Combes who had emigrated to America a generation before, and portraits of some of the family then living in Edinburgh. Besides these, there was a portrait of "Black Hawk," a Red Indian chief.

We placed the chief on one side, the Edinburgh portraits on the other, and those of the descendants of the American emigrants between, and all agreed that the deviations from the original family type were in a direction towards that of the Red Indian. Mr. Combe maintained that this is generally the case, and I agree with him. in regarding the typical "native American"-that is, the descendant of early English settlers-as displaying physically (I do not say intellectually and morally) a notable degree of reversion or rather

deviation-towards the aboriginal type displayed in the best examples of Red Indians-i.e. the old fighting chiefs.

Now, what is likely to follow from all this drying up of fibre, this development of constitutional intensification, this general inflammatory exaltation, or Americanitis?

I think that it must develop, is developing, and has developed, constitutional chronic disturbances-in some cases amounting to disease which may be curable by change of climate; the most effectual change being a return to that which produced the old stock.

My prophecy, then, is that American physicians will presently discover this, and recommend their well-to-do patients-those who have worked as only Americans in the pursuit of wealth do work-to turn to the land of their fathers, to breathe the soothing humidities of its anodyne atmosphere, and thereby double the remaining years of their lives, which I believe an overworked American of sixty years of age may do, and when he understands this subject and has sufficient means will do, to such an extent that Old England will become the sanatorium and final resting-place, first of her American children, then of Australians, and finally of all the rest of the con tinental world, when her mission of overspreading it is fulfilled,

MR

FLAMELESS GAS BURNING.

R. FLETCHER, of Warrington, whose blast gas-furnaces, solid flame burners, &c., have done so much in extending the use of gas as a source of heat, has, in the course of some lectures on the subject, shown a striking experiment which has been described in the newspapers in a manner that must have puzzled some of my readers.

Thus The Athenæum of July 22 tells us that "A gas flame was directed on a mass of iron wire until it became red-hot; a blast of air being turned on, the flame totally disappeared, but the iron fused and ran into drops. It was evident that the highest heat was obtained when the flame was entirely absent."

This would have been natural magic with a vengeance had it been done as the writer in The Athenæum states. Anybody acquainted with the rudiments of the subject will see the absurdity of such a description. Had Mr. Fletcher turned an additional blast of air on to a flame of gas already in sufficiently full combustion to make the iron red-hot, he would have cooled both the flame and the iron, Had the blast been sufficient to cause the flame to "totally

disappear," he would simply have imitated the very commonplace experiment of blowing out a candle. Rumford's axiom that the air supplied to a fire beyond the quantity required for complete combustion "is a thief" is now too well understood to need further demonstration.

What Mr. Fletcher actually did was this. He first exhibited a luminous flame wherein the supply of air was insufficient to effect the immediate combustion of the carbon in the gas; then he gradually supplied more and more air until the white flame was extinguished, and only the blue flame, indicating complete combustion, remained. This blue flame made the iron red-hot. Having thus adjusted his supply of air so that it should neither be in such excess as to cool the flame nor so deficient as to allow the flame to precipitate solid carbon particles, he stopped the supply of gas for a moment by pinching the flexible tube which conveyed it to the jet; the flame issuing from the jet was thus extinguished, but the gas, mixed with just a due supply of air, dashed against the extended surface of a red-hot ball of fine iron wire. What happened then? Simply that the combustion of the gas (ie. its combination with the oxygen of the air blast) occurred not at the nozzle of the jet, as when a match was applied, but on the actual surface of the red-hot wire which did the work of the lighted match in starting this combination or combustion. A flame actually existed, but only on the immediate surface of the wire, and being thus localised the heat evolved by the combustion was applied directly where its work was required, and none was wasted "in the desert air" between the nozzle or jet and the surface of iron, i.e. there was no flame radiating wastefully.

But why did not the flame rush back from the red-hot wire to the nozzle, as it does when we use a match? This, if I understand the descriptions rightly (for I have not witnessed the experiment), was due to the velocity of the issuing gas exceeding that at which the ignition of the flame proceeds. In one of my Notes in last January number, page 120, I described the experiments of MM. Mallard and Le Chatelier, which proved that the maximum velocity of propagation of the explosion of a mixture of coal-gas and air is 3 feet per second. Ten times this velocity is easily obtained in forcing gases through jets that have sufficient aperture to allow their free motion. Therefore, when the mixture of air and gas rushed against the red-hot wire and inflamed on its surface, a contest or race commenced, the flame ran back at the rate of 3 feet per second, but the gas rushed forward at greater speed, and thus the flame

could not get away from the surface of the wire against which the gas was impinging at the greater velocity.

It

There is more in this than a mere sensational experiment. indicates one of the directions in which all improvements in the economical application of gas-fuel (ie. the fuel of the future) should proceed, viz., that the combustion shall occur just where the heat is required for doing its work, and that it shall do its work there with the smallest possible amount of wasteful radiation or convection or conduction.

A

THE INTERNAL HEATING IN THE BESSEMER PROCESS.

N interesting illustration of the effectual application of the principle of economical combustion above enunciated is afforded in the Bessemer process.

The "converter" is a pear-shaped vessel made of stout iron plates duly bolted together and lined with a refractory material (ganister in the old-fashioned converters, or Thomas and Gilchrist's basic lining of lime, magnesia, &c., in others). The bottom of this vessel is a sort of colander perforated with holes about large enough to admit a man's little finger. These communicate with a blowing engine. The converter is charged by turning it on its side and pouring into its open mouth from five to ten tons of melted pig-iron. This is done while it is lying over, side downwards; thus the melted metal occupies the hollow in its side and does not reach the bottom.

Then the blast is turned on, and the ponderous vessel, actuated by hydraulic machinery, is turned slowly over to an upright position. Now the melted iron stands over the colander, but the blast is so furious that none can run through the holes. Tons of liquid metal stand on air, or I should rather say, dance on air, as the liquid is flung upwards with furious commotion and its gravitation brings it down again towards the openings, but not so rapidly as the blast ejects it.

At first we might suppose that these torrents of cold air would cool the melted metal, but not so; it grows hotter and hotter, and at last attains a temperature far exceeding the possibilities of any foundry melting furnace; it becomes much hotter than the melted steel in the Sheffield crucibles.

The reason of this is that pig-iron contains variable quantities of silicon and carbon, two combustible elements having some curious chemical resemblances. When in Sheffield I analysed all the brands of "Bessemer pig" used at the works of Sir John Brown & Co. I

found that their average percentage of silicon was 2.84, and of carbon 319. In a charge of six tons this gives an absolute weight of effective fuel amounting to about 8 cwt. The "blow" lasts about twenty minutes; the silicon, being the most combustible, is first burned, then the carbon, and both are usually well burnt out. Now, these combustibles are in such combination with the iron of the pig that they form a portion of the metallic liquid through which the air is forced, and thus their burning takes place intermolecularly (if I may be allowed to use such an adverb), and therefore the heat does its work even more directly than in the case of Mr. Fletcher's experiment described in my previous Note. There the combustion occurs on the surface of the iron; here, within its actual substance. It is not at all surprising, therefore, that 8 cwt. of solid fuel thus burned in twenty minutes should raise the melted metal to the temperature above described.

I have watched the process very often, and have seen the iron not merely melted but volatilized, driven off as gaseous iron, forming red clouds of condensing and oxidized iron vapour floating above the shaft into which the huge flame is rushing and roaring forth from the mouth of the converter.

METEORIC HAILSTONES AT THE BRITISH ASSOCIATION.

Y Science Notes for June, 1881, commenced with an account of M. Schwedoff's hypothesis concerning the meteoric origin of hailstones. At the recent meeting of the British Association this theory was brought forward and supported by Professor Sylvanus Thompson. Considerable discussion has since arisen, the highest authorities being unmercifully opposed to this "manifest absurdity."

Sir William Thompson demonstrated the impossibility of a cosmical hailstone reaching the earth by proving (mathematically, of course) that in passing through our atmosphere with planetary velocity, the hailstone would perform 13,000 times as much work as would raise water one degree Centigrade, and therefore, of course, the ice would be melted, volatilized, and dissociated into its component gases, &c. &c.

When Sir William Thompson demonstrated mathematically the dimensions of the ultimate atoms of matter, he was triumphant, and remains so, seeing that nobody has ever seen these atoms, and there is no proof (except mathematical demonstration) of their existence. Therefore they may have any size or shape, or whatever else the