Scientific and Useful.

Lake Wakatip Mail, Issue 1581, 18 March 1887, Page 4

Scientific and Useful.

TT.VAR PHENOMENON. From Greifswald, in Germany, a beautiful lunar phenomenon is reported. The crescent clearly defined was in the south-western heavens, when maidenly at its right side an enlarged reflection of the "rescent appeared, just as sharply defined and shining as clearly as the original crescent, which it gradually seemed to embrace. After some minutes there appeared on the left side a further reflection of this original image, but less bright and distinct. Both images remaiued visible for a considerable time, and then faded gradually away with the deepening darkness, leaving the crescent moon shining brightly as before. NEW APPLICATION OF SLICTBICnY. Professor Thompson has demonstrated before the Society of Arts, Ne» York a novel application of electricity by pheing pieces of metal, end to end, under a forcible pressure, and passing an electric eurrer.t through theui. Perfect weldings are affected even between metals otherwise incapnMe of being welded together, or between different metals. To weld steel of 1| inch diameter a current of 6000 amperes, having an electro-motive force of half volt, was necessary. It is stated that the use of thirty-five horsepower for one minute will weld that thickness of steel without any blows or the application of other heat. Steel also may be welded in this way to brass. TO TELL THE AGE Of EGGS. We recimmend the following process (which has been known for some time, but which has been forgotten) for finding out the age of eggs snd distinguishing iho-e that are fresh from those that are not. This method is based upon the decrease, in the density of eggs as they grow old. Dissolve two ounces of kitchen salt in a pint of water. When a fresh laid egg is placed in this solution it will descend to the bottom of the vessel, while one that has been laid on the d*y previous will not quite reach the bottom. If the egg be three days old it will swim in the liquid, and if it is more than three days old it will flont on the surface, anl proj-ct above the latter more and more in proportion as it is older.—La Nature. DETECTION OF LEAKS IN WATER YAIN3. The m;crophono is now bei<-g used in Germany for the purpose of (Meeting loss of water in town mains. The apparatus consistsof asteel rod.whichisplaceduponthecock in the neighbourhood of which the leak is

su«prcted, and a microphone attached to the upper end of the rod. A dry buttery and a telephone complete equipment. >"o sound is heard in the telephone it the cocks are closed and no leak occurs ; but a leak of even a few drops through a badly-fitting eeck causes sufficient Tibration in the pipe to affect the microphone, and to give audible sounds in the telephone. At a recent me-ting of gas and water engineers in Eisenach it was stated that the apparatus is so simple to handle that, with a little practice, ordinary workmen are able to detect and localise any leak. BrBMAMNB BOAT. With reference tothe submarine boat which has attracted some attention in the d:ily papers, it may be as well, says the English Mechanic, to point out that the idea is certainly more than 250 years old, for in the reign of James I. a Dutchman named Drebbel, constructed a boat which traTclled under the surface of the Thames. Since then many submarine vessels hare been designed, but none of them has yet accomplished what has been done by Prof. Tuck's Peacemaker in the Hudson river, New York. That vessel apparently dives with ea-e, and returns to the surface as desired. A very powerful submarine vessel is being built to the designs of Mr Nordenfelt, with engines of 13CK) horsepower, and it wiil probably be reaiy for trial in Southampton Water in the spring. CHINESE BTHAW SHOES. We (Scientific American) understand that Dr Macgowan has sent to the Agricultural Bureau, through Consul-General Kennedy, of Shanghai, a collection of shoes made of rice straw, and worn by labouritg p-op'o in the south of China. Dr Macgowan sends them, suggesting the introduction of rico straw shoe-making into the rice producing regions of the South. They are made by women and others who are too feeble for more active employment, which circumstance and the abundance of the material, render them rery cheap—from one to 12 cents a pair! Dr Macgowan suggests also the introduction into nurseries for children's wear of these straw shoes, that more freedom be allowed to the feet of our children. The highest priced shoes—l2 cents—ure made ot mat grass (Arttndo mites), which Dr Macgowan says should be acclimated in the south, and that mat-making should prove a profitable industry. TO DISTBOY MOSB ON i'RCIT-TUEKS. Nothing is easier than to destroy moss on the branches of fruit trees. When the branches are wet, fresh-slaked strong lime thrown freely amongst them will adhere and destroy every vestige of moss. This is far more effectual than using the lime as a wash —applying it with a brush. The falling of the lime to the ground is also beneticial. In all gtrdens wiiere moss is prevalent lime should be annually dusted amongst the current and gooseberry bushes and fruit trees, after they have been pruned and before the ground is dug, and cleaner branches, healthier trees, and finer fruit will follow. The lime is also useful in protecting the fruitbuds from birds. A man will do more execution in one day in destroying moss by thus dusting with lime than will auother man

iu a week with the " whitewash brush." THE HYGIENE OF CTCLINO. According to Dr Kunze, of Halle, cycling is a health-stimulating exercise, which ought to be commended by medical men. It is a powerful means of strengthening the human body, and may even be considered an exercise acting as a preventive and ctiratire, of no mean order, ot certain bodily ailments. Looked upon in the latter light, ryeling is a kind of gymnastic exercise, possessing specific effects which are absent in ordinary gymnastics. The Telocipedist (especially the bicyciist) Id'rn- first of all, the art of balancing himtelf by practising it on an instrument as sensitive us it is easily overturned. To acquire it, it is necessary to call into precise action certain muscles, every individual muscle being strained to do its particular work. Those who are thrown from a bicycle as a rule—certain eventualities against which even the most skilled Telocipedist cannot guard excepted—do not yet possess the required ability to balance themselves. This latter acquirement is of great use in practical life. .Those who possess it will be able to jump ditches with greater precision and safety, pass Blong narrow paths, mount more difficult staircases, climb up and descend precipitous mountains, and will also carry themselves more erect, than those who do not possess this power of preserving an equilibrium.