SCIENCE NOTES.

Otago Witness, Issue 2669, 10 May 1905, Page 68

SCIENCE NOTES.

— Under the heading "Are ' Masonry j)ams Safe?" the Leeds ' Mercury of March 25 writes: — The Egyptian Government has decided to postpone the enlargement of the 'Assouan dam, in consequence of a new theory on the stability of masonry dams which has been propounded by two English mathematicians. Ifc is an astonishing announcement, and tho discussion which will "ensue is likely to ba one of the most important that -has taken place in practical science for a generation or two. The .importance of the new theory will be understood when it is realised ih&t masonry dams are holding the waters of some of the largest" reservoirs in this country, as well as all over the world, and if it be established will alter the construction of waterworks considerably. Sir ' William Garstin; the able engineer of the Egyptian irrigation scheme, concurred in the proposal of Sir -William Willcocks to raise the dam at Assouan so as to enable it to hold .water 7 six metres above the present maximum level in -the reservoir, and according to all accepted theories there was no risk *o the structure in doing so. But in ib-e flight of the new theory regarding the stresses upon masonry dams, he has seen *hjs necessity for suspending operations until further discussion has ' enabled engineers to come to a conclusion on this most important question. The new theory is propounded by Mr L. W. Atcherley, Demonstrator in Applied Mechanics to the University College, London, and Mr Karl Pearson, Professor, of Applied Mathematics and Mechanics at the same college, and -their reputation is so high that, in the words of Sir , William Garstin, "any theory ' advanced by them must merit the most serious attention." These two mathematicians -have come to the conclusion that Ithe vertical sections of a dam under water pressure are more severely strained than Ithe horizontal eection^, and that while- a

H am designed under the' rules hitherto ap- _ (plied xnay be- safe as regards cracking horizontally., it may, nevertheless, be liable to do so -vertically. Hydraulic engineers, as well as mathematicians, .in England and iFranoe are engaged in considerinff_thjsu>-%nc' reaching proposition, anpL^tfee^^esults of

their examinaii^3r"aifo^discussion will indesigns for masonry dams. —"bit William Garstin called in Sir Benjamin • {Baker, who made a special journey to Egypt for the purpose of examining the effect of two years' regulation of the Assouan ■Dam, and the result is the postponement of the extension scheme. The theory is too abstruse for any but specialists to coinyprehend, but it is of world-wide importance, and may have far-reaching effects on all waterworks engineering. " —In '-'Looking Backward," by Edward •Bellamy, issued some, years ago, the author ,'putlines an apparatus by which music of lany character to suit the taste of the subscriber may be had by the mere pressing yjf a button conveniently located in the " library or the parlour of a home. This tlream' (says the Scientific American) is about to be realised, as- a company to promote such an invention has been recently 'organised in Boston, Mass., composed of moneyed men of that city, Philadelphia, and Baltimore. This company has secured ,the rights to the invention of Thaddeus 'Cahill, who has been at work on the matter for nearly 15 years, and recently demonstrated its successful operation at Holyoke, Mass. ,The list of names of those behind the scheme presents a number of the strongest -financial men of the cities named, and it is announced that fhe first service .tvill soon be established in Boston and 'afterwards extended to other cities. One of the officers of the company stated that the appai'atus had been examined by Lord [Kelvin, when he paid a visit to America jßome time ago, and he pronounced it en-

tirely practical. The corporation will be known as the Cahill Teleharmonio ComJpany, the controlling concern being the (New England Electric Music Company. |Mr Cahill, the inventor, is a graduate of £)berlin College. The difficulty of making Sin instrument to do this work has heretofore been found in securing the means of accurately registering the great range # of /vibrations indicating the different musical Jnotes, some being as low as 16 per second fend others as high as 8000. It is planned to Jiave six classes of selections, and the annual fcost of the subscription will be" from 50dol aupward. The service will/ become cheaper, it is promised, as the number of subscribers increase.

— But for the electric telegraph it would ibe impossible to work railway traffic with any degree of frequency except at perpetual risk of collisions. With its aid theworking even of frequent trains in both over a single line (with passing Jplaces) has become absolutely safe — supMfiiftS vulgs /is* -obeyed, — while on. double

lines trains can he started one after another in the same direction at as short an interval as two minutes. Indeed, on the Central London railway as many as 31 trains have been got away from the Bank station within a single hour, following one another with perfect safety over the same pair of metals. This is the triumph of the "block system" of railway working, which was first put into operation by Messrs Gooke and Wheatstone on the Norwich and Yarmouth railway in 1844. The one weak link in the chain of the block system is that the telegraphic communications upon which its working depends must all be transmitted into signals through the agency of fallible human beings stationed in a series of cabins along the length of the line, while these signals in turn must by fallible enginedrivers be translated into those stoppings and startings of trains at critical moments upon which the safety of the passengers depend. It is an open question whether any mechanism which human ingenuity can construct can be less fallible than the human brain itself, but whereas human, failures are so varied and erratic as to be incalculable, the failings of mechanism can be foreseen and guarded against, so as to produce a system in which the chances of dangerous error are infinitely small. — March Windsor Magazine.

— Niagara River develops eight and a-half million continuous horse-power. This rate of work ' is entirely beyond human conception, but some faint idea of it may be got by reference to the amount of coal that would be consumed to develop energy at [ the same rate. If 21b of coal were burned per horse-power per hour, the weight consumed in that time, to equal the work of Niagara River, would be 8500 tons. Continous work for one year at this rate would require 74,460,000 tons of coal, or more anthracite than the United States produced in the year 1900, when the entire output was 57,464,235 tons. This prodigious power, except, the relatively small amount that is d«voted to useful work, is now continuously expended in__earvihg a deep, narrow channel ! through the" strata of rock, about 20 miles Wide and more than 300 ft thick, that sepai rate Lakes Erie and- Ontario. Already the strong hand of the water, armed with stones | and silt, has carved the great canyon of the lower river, about , six miles long, from Niagara Falls to the foot of the escarpment at Lewiston and Queenston. In many frhotusands of years to come, if the work of the river is not interrupted, the 14 miles of canyon that remain to be excavated between Niagara Falls and the foot of Lake Erie will be completed. Then that lake will narrow down to a river and the falls will be transferred to Detroit River. — Cassier's Magazine. — That we sleep is one of the indubitable facts of life. But why do we obey this 'command of physical and intellectual repose? The various answers to this question are summarised by Henri de Parville in the Correspondent, Paris. Some physiologists say that we sleep because the circulation of our brain diminishes and the blood vessels relax, emptying themselves partially of blood. Thus sleep is_^artiaP cerebral anemia. This^iheorf^wTtn some experimenjejs=*-fe€ts~~given place to that of jaugeitrta^fatigue. A muscle, when it has worked a great deal, refuses to perform additional labour; it is exhausted, and it no longer obeys the will. This is the case with the brain; after a certain period of work it has need of rest. The cerebral cell becomes incapable of performing work, and the human machine stops, until such time as the blood brings to the exhausted parts new food, new agents of excitation, when the intellectual and physical life is again taken up. There is another theory, that of intoxication or poisoning. According to Professor Bouchard our body is a poison laboratory. During our waking hours, we are continually manufacturing, in our organs, in our glands, in our intestines, poisons of various sorts, which are distributed through the blood and are eliminated by the kidneys, liver, lungs, skin, and other organs. " "When the poisoning is complete we" sleep. During sleep bodily activity is small, and we are able to get rid of the poisons, and as this takes place we gradually come back to consciousness. Still another theory is that of the neurones. For example, modern miscroscopic work has shown that the crust of the brain is comnosed of a multitude of cells provided with innumerable prolongations resembling spiders' legs. These fine prolongations are called neurones. Each cell, however, is supposed to have its individual life, at the =ame time extending its neurones in every direction. The neurones thus come in contact with each other, and the cells thereby communicate one with another, from all of this activity arising what we call the cerebral life. When exhaustion appears the cells draw in their prolongations, cut short their relations with the other cells, and calm succeeds the storm. Each cells sleeps and we sleep. There is still one other theory which M. de Parville considers worth mention, especially in view of the fact that it is the very latest. This theory is expounded by M. Claparede, of Geneva. According to this scientist, all previous theories are wrong, because the greater the fatigue the greater should bethe intoxication and the more profound the sleep. Now experience shows us that the contrary in many instances is the case, for frequently during extreme fatigue one cannot sleep at all. Therefore, M. Claparede says that sleep is a normal function which is designed to prevent, or inhibit, the work of the human machine. We do not sleep because we am poisoned or fatigued, but we sleep in order to be neither of these things. In other words, we sleep by instinct.

— Ships will soon have- ears — ears that will hear the appi-oach of a torpedo boat that the captain cannot see, or that will henr the sound of the fog-bell, ox* the waves Seating against a clanjferous, rogk. ojj g

stormy night. These electrical ears, as they are described by the American Telephone Journal, ' are more sensitive than human ears, because the sounds they will hear are sounds which travel under water, a medium which transmits sounds better than air. It is this superiority of the water as a sound-transmitter that has bronght about the new invention. It is called a "subaqueous telephone." Its principal elements are delicate transmitters, or microphones, attached to the hull of the vessel below the water-line. These sensitive instruments intercept the sound-waves as they traverse the water and transmit them by regular telephone wires to the captain, who, wiLh receivers at his ears, is listening in the wheelhouse. It is expected to perform a most valued service in averting collisions. A type of the subaqueous telephone which has been adapted to fishing-boats or small vessels of any kind consists of a receiving-box with a ball-receiver, which is lowered into the water. It is obvious that some sounds would be too delicate to penetrate the skin of a vessel, and might not be heard by a receiver located on the inside. Henoe ifc is that the receiver is .lowered directly into the water, and picks up sounds of comparatively small intensity. In case of emergency, where a ship is not supplied with receivers located on its hull, by lowering ono of these ball-receivers first on one side of the vessel and then on the other, and noting the difference of intensity of the sound, it is practical to locate the source, whether it be the signal of a fisherman in a dory, a bell-buoy, or any other signal.