Science Siftings

New Zealand Tablet, 18 February 1915, Page 51

Science Siftings

By * !VdijT.*

A Valuable Sewage Farm.

The city of Berlin affords an excellent illustration of the enormous development to which the pursuit of sewage disposal by sewage farming has led. The city itself covers an area of about 20,000 acres; its sewage farms are no less than 40,000 acres in extent. In a way the Berlin sewage farm is a gigantic real estate speculation. Ultimately the city will sell the sewage farmland at large profit and turn to modern biological methods.

The Sun’s Losses.

It is calculated that the sun loses a mass equal to that of our earth in thirty million years. If it be assumed that the mass thus lost is gravitational, it follows that the length of the year increases by six seconds in a million years, and that in the same time the mean longitude of the earth is affected in such a way as to produce a variation of one-tenth of a year —i.e., a retardation of thirty-six days in the seasons. Such variations are too minute to be observable. In stellar systems possessing a higher temperature the effect would be much more marked for the energy radiated by a body varies as the fourth power of its absolute temperature.

Coal-Cutting Machine.

Revolutionary changes in coal-mining methods are promised upon the general introduction of a coal-mining machine developed by Mr. 11. A. Kuhn, a Pittsburg mining and mechanical engineer, who has spent more than ten years in perfecting the machine. The device, constructed of structural steel, can attack the coal seam in any position, moving up or down or in any direction in which the seam leads. It takes out more than 90 per cent, of the coal in the ground, whereas the best practice of to-day seldom recovers more than 70 per cent, of the coal. It is stated that the machine has demonstrated that it can cut the cost of mining coal by half. It is said that ten of them can produce over 1000 tons of coal a day. Only two men are needed to guide the mechanism of each machine, which takes the coal from the seam, cuts it, puts it on a conveyer, and loads it in a pit car without a human hand touching it. Electricity or compressed air can be used, and so little power is required that the cost thereof is less than •one-halfpenny a ton for each ton of coal mined.

Queer Freaks of Wireless.

Wireless telegraphy has many apparently mysterious qualities for which scientists have been unable satisfactorily to account to the layman. Failure to operate on account of the conditions of the atmosphere has been the chief source of annoyance. Another fault, which has recently been remedied, is in the absence of secrecy in transmitting messages. Lightning and other elec-

trical disturbances have also caused some inconvenience, but in the event of a storm the apparatus is ] now usually grounded in order to prevent injury. It is reported that lightning will seriously injure, if - not entirely destroy, instruments, even though it plight strike at a point five •or ten miles distant. ..Why the wireless works better at' night or in cold weather rather than hot, why transmission is better on the Pacific Ocean than on the Atlantic, or why Communication is better in one direction rather than in another have all been puzzling questions. Those elements, of unreliability and disappointment are now disappearing, however, and the confidence of the public has been won.