SCIENCE NOTES.

Otago Witness, Issue 2471, 24 July 1901, Page 70

SCIENCE NOTES.

—It has been found that arsenic occurs in easily detectable quantity in the hair of persons who have been taking the drug either medicinally oi accidentally, as in the cuse of beer. A method of examining the hair by means of an ammonia copper solution containing an excess of the precipitated copper oxide has been recommended. In patients taking email doses, the medulla of the hair will remain unchanged, as far as a half-inch objective is concerned; but when viewed by a sixthinch objective the small green particles of arsenite of copper are seen appearing as green grannies without definite shape or formation. This simple test might prove useful forensically, says the Lancet. In some patients the quantity of arsenic found is too minute to be estimated, but in a patient wb"> is takiag the drug medicinally the hair was found to contain arsenic in the proportion of 0.3 in 10,000. One of the patients who had been drinking arsenical beer had pressnt in his hair the same proportion of arsenic, while another showed as much aa 1 part of arsenic in 10,000. The method employed for the estimation of arsenio consisted in fir3t destroying the hair by means of fuming nitric acid, then dissipating thf> excess of nitric acid, after which the product is transferred to the Marsh apparatus.

— Since the kite has entered into the domain of science, it has been greatly perfected. The aim has been to give it considerable ascensional force and great stability, so that it may be used to carry into the air apparatus u?ed in meteorology and photography without fear of disastrous fall. But hitherto little has been done to utilise its force of traction, which may be considerable if it is given sufficient height. Recently, however, experiments in this direction have been made on the Moselle by a man who, having flown a Malay kite two metre 3 (6gft) in length, caused it to tow against a somewhat swift current a boat holding six persons. « The wind was quite strong, and it was very easy to increase the force of traction by flying several kites. Those of the Hargrave system would perhaps be the best, lince one of this kind, having a height of 1.4- metres (4^ft), can scarcely be held by two men* wiiea euouah. ooxi hag

been paid out. The retaining cable must possess great strength, especially if it is to hold several kites, or the tractive force may rupture it. It is evident that in this original mode- of lojspmotion the direction of the wind y>laj» an important pjut, for if the angle that it nuke?' with the watercourse exceeds 45cleg or 50cleq, the boat i* hard to steer, and moves slowly. Nevertheless this method of seeking a continuous current of air at a certain height is of Uie greatest simplicity. If it is not used, the reason i« doubtless that it has been thought that not enough force would be developed by it. Still, the results already obtained i'ic interesting. — Cosmos.

—Dr Miller, of Berlin, has described more than 30 s-pecies of the microbe? of the digestive system inhabiting the oavity of the human moujj), some of them also to be found on the- human skin ; others, which were found about the teeth, were peculiar to the mouth and were not met with anywhere else. Several of thp specie^ charac teristic of the mouth made their waj t'eep into the digestive organs, and were recognisable in the stomach and the intestines. The stomach, with its acid contents, rfi'tied conditions affecting in a quhe exceptional way the development oi microscopic growths. Many kinds of bacteria could not endure an acid environment: still, the bacterial f-j stem of the human stomach was pretty noli, 50 different species having already been distinguished, most of which were not found elsewhere in the digestive system. In the stomach, and still more in the small intestines, bacilli were the predominating form of microbe, the number and relative proportions of micrcboa in the small intestine varying with the food paten. Meat and vegetable diets respectively stimulated the development oi special bacterial forms, though even when the diet was unaltered, noteworthy fluctuations in the microbian population were observable. From the smaller intestine the microbes passed to the larger, where they were joined by a great number of new kinds. Of all the parts of the human body, the large intestine was \mdoubtedly the most abundantly teeming with these growths. It was inhabited by about 4-5 species of microbe, chiefly bacteria, turong which bacilli were much the most numerous. The large intestine began to be inhabited immediately after birth. Even on the first day of life, before any food whatever had been taken, a fairly great variety of microbes were to be found there. When the child was suckled the population of the laige intestine very soon underwent a change. It became more uniform and w?.s composed mainly, and sometimes almost exclusively, of a particular bacillus. In children fed with the bottle, on cow's milk, this bacillus was found too, but in smaller numbers, the large intestine in these children being much richer in microbes of various types. After weaning the abundance of microbes became much greater still. The number of distinct species of microbes to be found in a man in Health could not be exactly estimated, but quite roughly and provisionally might be put between 60 and 70.

— The successful mounting of the gigantic 4-0-inch lefractor in the Yerkes Observatory at Williams Bay, Wisconsin, U.S.A., ranks among the greatest achievements of the modern mechanical engineer. In this telescope the "spurious disc" of a fixed star, which would appear' as a mere point ol light but for the effects of diffraction, has a diameter of less than one-eighth of a second of arc, and this apparently real image will have a breadth at the focal plane of about 1-2500 inch. The focal plane of the instrument is distant 32ft from the point about which it turns: the spider-threads of the micrometer used for star measurements have an average breadth of l-6000in ; and the weight of the moving portion' of the telescope exceeds 22 tons. Given all these facts, it is possible (says the Morning Post) to state the problem which Ambrose Swasey and his coadjutors were required to solve. It was necessary for the observer to be able to move this mass of metal and glass in opposition to the earth's motion so steadily that a star disc l-2500in in diameter should never slip off a spider-thread less than half that breadth, and carried at a distance of 32 feet from the centre of motion. An invention emanating from the fertile brain of Sir Hiram S. Maxim is sure to command respect. Although co well known as the inventor of death-dealing engines, he is no less tnjccessful in his inventions for the good of the public in the peaceful walk of life. One of his latest achievements is the production of an incandescent electric lamp which bears his name. This lamp only required to be more widely known to become universally adopted, and at the same time give an impetus to electricity as an illuminant. The price of the lamp is no more than that of other lamps of a similar kind, and it has the advantage of giving forth the same amount of light at a saving of at least 25 per cent, of the amount of current consumed in incandescent lamps now in commercial use. The filament is composed of practically a new material of groat durability, which gives a longer life to the lamp and les3 discolouration to the globes. —By the improvements in his apparatus, and particularly by the use of the cylinders in place of the vertical wire, Mr Marconi has, says Engineering, been able to render his apparatus far more portable. He has constructed a steam motor-signalling car for use with an army. On the roof of this oar, which is of the omnibus type, there is placed a cylinder, which can be lowered when travelling, its height being only six or seven metres, and by this means communication has been easily carried out with a syntonised station over a distance of 50 kilometres (31 miles). A 25-centimetre spark induction coil, worked by accumulators and taking 100 watts, is used for transmitting. A strip or wire netting laid on the ground is sufficient for earth connection, even when travelling, or in place of this the electrical capacity of the boiler of the car can be used as "earth."

— The Car« to Cairo railway will cross the Zambesi River at the Victoria Falls, approximately 300 milos north-west of Bvilawayo. It would appear as though a foreseeing providence had arranged the matter, for only a few hundred yards below the Falls, and at the commencement of a wonderful gorge that goes twisting away for 30 miles, the railway engineers have chosen a spot where a single span of 600 ft will bridge the whole river. All the exposed banks of river, chasm, and gorge are of solid black ba<-alt, substantial material to found the piers upon ; and we believe it is intended to employ as little superstructure as possible in the construction. The trains will creep across this chasm at a height of nearly 400 ft above the level of the water rushing below, and po close to the Falls themselves that the driving spray will fall upon the carriages a3 they turn on to the bridge. The clear jb»M p| the water over the fall is 375 ft;

J Niagara at the Horseshoe is 165 ft. The j lip or edge over which the water thunders I down into that chasm is one mile and 200 yards long in almost a straight line, while Niagara is under 900 yards along the curved lip. — Illustrated London News.