THE WORLD OF SCIENCE.

Waikato Times, Volume 93, Issue 14540, 11 December 1920, Page 9 (Supplement)

THE WORLD OF SCIENCE.

*. BETTER CANNING. In the “Journal of Industrial and Engineering Chemistry” an announcement is made that the Glass Container Association proposes to give prizes to any students working for a degree in college or university, for the best suggestions for various ways of safer canning and the use of more convenient glass receptacles for canned food. The Glass Container Association's research programme is an outgrowth of prohibition, which deprived a number of bottle manufacturers ot a large share of their profitable business. They now turn to science to aid them in finding ways to continue Hie profitable manufacture of glass containers. The contest announced carries with it awards of from 50 to 150 dollars, and the results of the research investigations are lo be announced in essays along lines of the better preparation and packing ol foods for canning purposes with particular reference to Hie use of glass. THE USE OF WET AND DRY SAND FOR CONCRETE Recently several series of tests of concretes made in the United States made from sand and gravel have been carried out in Hie United States, using various proportions of cement to

aggregate from 1:11:3 to 1:3:6 and

with the extremes of flowabilily used in practical concrete construction work. The results of those tests emphasise a feature of considerable importance to Hie contractor. When aggregates are proportioned by volume measure, as is customary on most constructional work, it is found that the use of wot aggregates requires from it lo 1 bag more cement per cubic yard of concrete than do dry aggregates. Sand is generally wet or at least moist when used so that the full difference may never be apparent in field

practice, yet the use of sand from a pile which has just been exposed to rain will result in the employment of more cement for a given volume of concrete than would have been the case had Hie work been done on a dry day. The excess strength resulting from the increase in cement is unnecessary, providing that designed strengths were obtained with the drier materials. As above mentioned, this increased quantity of cement may be as high as one bag per cubic yard of concrete, and Hie increase in strength, due to the added cement in a cubic yard of concrete made with wet aggregates, is roughly proportional lo Hie increase in cement. Therefore, if there is a marked increase at any time in the moisture carried by Hie sand, Hie tendency on Hie job should be to use larger volumes of sand in the batch. Marked improvement in Hie working qualities of the concrete will be noted under usual conditions when the relative volume of sand is increased and Hie gravel proportionately reduced. With well graded river sand and gravel the “oversanding” may be beneficial up to the point where the volume of sand in Hie batch is equal to the volume of Hie gravel. Such concrete will not segregate for maximum llowability commonly used in construction work; it will be easier working, Hie quantity of cement required per cubic yard will he slightly less and there will he no reduction, in compressive strength.

The pressure produced by Hie blow of a whip lash lias been investigated by a French humanitarian. By receiving the blows of a whip lash on a surface of soft clay and measuring the depth of penetration, It was a simple matter to determine how many kilograms or pounds were required to effect Hie same result by simple pressure. The force of the blow was found lo be far higher than supposed; it varied from 7? to over 300 pounds. The plea is made to spare Hie uncomplaining servant of man and |o practise kindness and restraint in Hie use of Hie often brutal whip.

X-rays have been applied to the disclosure of ancient paintings. In old times a painting was often obliterated by a coal of ground colour and a second painting made on the new surface. Now by the use of the X-ray some of these ancient, paintings have been photographed through the overlying and more recent picture with interesting and important results. In one case an absolutely invisible picture has been radiographed and , in another case numerous restorations and changes in a painting by an old master have been disclosed. It, is believed that tiie same method niay prove of value for the study of palimpsests, manuscripts which have been erased so as to permit the parchment to be used for oilier writing. Often it happens that the old erased matter can be brought to the light of day, and in this way priceless finds are pos•ible«