Science Sittings

New Zealand Tablet, Volume XXXV, Issue 46, 14 November 1907, Page 35

Science Sittings

By 'Volt*

Explosions in Flour Mills The riskjs of explosion in flour mills are discussed in ' Knowledge and Scientific News.' Mr. •S. F. Peckham calls attention to the occurrence of dangerous dusts in other factories. After the terrible explosion in 1878 in Minneapolis, in which three flour mills were destroyed, a simple apparatus was devised by Professor Beck' for testing the explosibfiity of the dust, .and it was demonstrated that the ignition of 2oz; of flour in a box containing two cubic feet of air, would cause an explosion of sufficient force to raise two men standing on the lid of the box. Hence a sack of flour ignited in 4,000 cubic feet of air, . would be capable of throwing 3,500 tons to a height of- 100 feet. The right - proportion of air to dust is necessary- for an explosion, just as in the case of mixtures ,of coal gas and air. With, this apparatus, Mr. Peckham has shown that the dry dust in the wood-planing factories can be /made to explode as readily as flour, and that, in fact, any dust that will burn, may become a source of danger. For • instance, an explosion in a confectionery works in New 'York was traced to the sugar powder, whilst dry soap' -was found to be responsible for a terrible fatality in a soap factory. Hence it is of the utmost importance . that no -dust should be allowed to accumulate in any factory where it is possible to prevent it doing so. . „: . Mining in Peru . "It is thought Vbhat the old Caylloma silver mines in Peru are probably situated at a greater elevation than aliy other considerable mines in vhe world. Their altitude varies between 14,000 and 17,000 feet. They were worked by the Spaniards in the sixteenth century, #and before that, it is believed by the Incas. An English company is now-preparing a hydro-electric plant for them This plant will be situated at an altitude of between 15,000 and 16,000 feet. It will .derive its power from a waterfall on /the Santiago river, .and in dry season from Lake Huaillacho, one of the sources of the Amazon. The power will be transmitted by cable about three miles. At the highest mines the pressure of the atmosphere is only eight and one-half pounds a square inch, and water boils twenty-four degrees below the ordinary boiling point. River of Salt Water . - One of the curious phenomena of geography is found on the southern coast of the island of CephaTonia,^ in G-reece. It is a stream of salt water which for an unknown period, has left the almost tideless sea and flowed inland with a volume sufficient to furnish water power to two mills. For some generations the mills were operated by undershot wheels, which took their power from this little river of ooean' water. They supplied flour to the people of the island until recently, but now they have been dismantled, owing to the competition of larger and better equipped mills. The sea enters the land at four points, where the coast is practically on a level with the salt water surface. The four initial streams unite to form the little river, that flows inland in a, broken • rocky - channel, until it finally disappears in the -limestone rock and sinks into the eartln This 'inland flow has continued almost certainly for several centuries. It is far too great for removal biy evaporation, chemical combination, or even physical absorption by pores or caverns " in the rocks. What becomes of the' water, that is constantly flowing inland and disappears finally in the fissures that have opened in the limestone ? The question has been the subject of much study, but no conclusive answer has been given. It _is probaibfle that there is an underground channel ' which carries the_water back into the sea at no great .depth 'below the surface. The constant influx of saltwater at Cephaloriia is duplicated, as far is known, at no other point in the" world. A Peculiar Book . s One of the most curious books in the world belongs to the De Ldgne family^ of France. This book "is neither printed nor written. All the letters are cut out of the vellum and interleaved. \witl£ a peculiar shade of blue paper/ The work is. so ; carefully 1 done, that the book is read with the greatest ease.' Rudolphus Ilr-' of Germany offered eleven thousand djecats for it ; but it: was not, sold. The most peculiar % thing jabout this volume is that it bears the royal arms* of England;- but "as far as can be traced it .has never been in that country,.