The Montgomery advertiser., 1903-09-27
SCIENTIFIC MISCELLANY
EFFICIENCY-STREET
 PAVING.
A cafe Explosive-Japanese Sword making-Red Rain in Australia. Illumination With Alcohol. Why the Intestines Are
 Not DiRested.

The electric discharge between two ves- sels of mercury in a partial vacuum Is the most efficient form of artificial light ing yet discovered. In a recent test by W. C. Geer, the mercury terminals were about four-fifths of an inch apart. and an arc of two inches in length was pro- duced by a direct current of no volts. Nearly 50 per cent of the energy sup piled was converted into visible light. Turning to other lights. the Geissler tube showed an efficiency of 32 per cent; the ordinary arc lamp, 10; acetylene gas 10; the incandescent electric lamp, .6; and the Argand gas burner. 1.6.
 An investigation of paving stones has been undertaken in Ireland by Professor Joly. He finds that resistance to wear va ries directly with the amounts of quartz and fel-spar contained, the completely crystalline igneous granites, etc.. being as a rule the toughest. Rocks that are de- cidedly porphyritic, porous or glassy are to be avoided. A certain coarseness of grain is usually desirable, as fine-grain- ed rocks like a certain Welsh diorite, are liable to become slippery.
 Ammonal, a new mixture of powdered aluminium and nitrate of ammonia, is claimed to be one of the safest of ex- plosives It is not liable to explosion by shock or friction, Is not readily fired, Is especially free from spontaneous decom- position. and is even credited with the rather surprising property of being un- affected by moisture. It Is fired with the usual percussion cap.
 The temperature limits of life are much more widely separated than we once SUD- posed. Bacteria are now known to develop and multiply at 72 degrees C.; and Pro lessor A. Macfadyen. of London, has ex- posed such organisms to 19o degrees G. below zero for six months without harm ing them, while they even survived 2oO degrees c. below zero.
 One of the most interesting of metallur- gical processes is the manufacture of Ja- panese swords A recent description states that the steel is produced in thin laminae from magnetic iron ores and fer ruginous sand, and the work upon the weapon begins with the fixing of one of these plates to an iron rod, which serves as a handle. Other sheets are soldered on until tho mass has a length of six to eight inches, a width of two inches, and a thickness of one- fourth to four-fifths of an inch Brought to white heat, the bar is doubled upon itself and hammered to it's original form, the process being re- peated fifteen times; and four similar bars are then heated and soldered, this process being repeated five times. These opera tions give superimposed layers so thin that sabre Is estimated to contain at least a thousand sheets of metal. Alter nate layers of iron and steel are some times soldered together, and veined ap- pearance is thus given to the blade.
 In their investigation of the rains of red mud that fell in Victoria early this year, F. Chaman and H. J. Grayson have found that the deposit in one case reached fifty tons per square mile. Much limonite was included, with many mineral fragments and diatoms. The material seems to have been carried by the winds from the vicin- ityl of certain swamps and salt lakes. which exist from 30 to 300 miles north and west of Melbourne, and whose margins had been made unusually dry by season of drought.
 With his improved lamp, L. Denay-