Science Siftings

New Zealand Tablet, Volume XXXVI, Issue 22, 4 June 1908, Page 35

Science Siftings

By VOLT

' Polling Dew ' Fallacy/

Although the poets have' spoken of the ' falling dew,' it is now a scientific truth that dew is for the most part formed of vapor rising from the ground. A proof of this is seen in cold weather, when the hoar frost (which is really frozen dew) is ~ abroad. If leaves are lying about, the coating of hoar frost is found 'on the underside of the leaf. Much of the moisture seen on the plants after sunset, however, is not dew at all, but is simply caused by the - exuding -of the watery juices of the plant. These form in little ' diamond drops,' which are of ten . mistaken for dew. The real dew, on the other hand, is generally distributed evenly over the whole surface of the leaf. Dew, in short, is simply the moisture of the earth and air, which, as vapor, is condensed into water by a fall in. temperature.

Cities Built on Islands.

Ghent, Belgium, is built on 26 islands, most of which are bordered by magnificent quays. The islands are connected by 80 bridges, having as many canals or waterways as streets. Ghent is the capital of East Flanders, lies on the Scheldt and the Ley., or Lys River, as well as _ on the insignificant Lieve and Moere, which flows through the city in numerous arms. Venice is built on a still more numerous cluster of small islands, numbering between 70 and 75, in the north-west portion of the Adriatic. Owing to the lowness of the islands, the city seems to float upon the sea. Amsterdam is divided by the Amstel River, and numerous canals into 100 small islands, connected by more than 300 bridges. Almost the whole city, which extends in the shape of a crescent, is founded on piles driven 40 or 50 feet through soft peat and sand to a firm substratum of clay. *

Meaning of Word Calibre.

There is surely no word in the nomenclature of guns, bigp and little, which has caused, and is causing, so much confusion in the l&y mind as the word calibre. The confusion arises chielly from the use of the term in an adjectival sense to indicate length, as when we say a 50-calibre, 6-inch gun. The word calibre as applied to artillery signifies essentially and at all times the diameter of the bore of a gun. A gun, .then, of 6-inch calibre is a gun whose bore is justr six inches. For convenience, and because the power of a gun, when once its bore has been decided upon, depends so greatly upon its length, artillerists are in the habit of defining the length of the gun in terms of the calibre. The six-inch rapid-fire gun, as mounted on the latest ships of the navy, is a trifle under 25 feet in length, and is, therefore, known as a 50-calibre gun. In the case of small arms, ,the calibre is expressed in hundredths of an inch, as when we say a 22-calibre or 32-calibre pistol, meaning that the bore is .22 or .32 of an inch in diameter.

Powerful Drops of Water.

A drop of water, even three or four drops, falling on the head, seems a thing unworthy of attention ; nevertheless, in China a slow and continuous dropping of water on the head has been found .to be a method of torture under which the most hardened criminal abjectly howls for mercy. When a professor in the Sorbonne stated this to his class recently one of his students laughed incredulously, and said it would take a good deal of that sort of thing to affect him. The professor assured him that even one quart of water dropped slowly on his hand would be beyond -endurance. He agreed to experiment. A quart measure filled with water was brought in, a microscopic hole was bored in the bottom, and the performance began, the professor counting. During the first hundred drops "the student made airy remarks. With the second hundred he began to look less cheerful, then gradually all his talk died away, and his face took on a haggard, tortured expression. With the third hundred the band began to swell and look red. The pain increased to torture. Finally the skin broke. At the four hundred and twentieth drop the sceptic acknowledged his doubts vanished, and begged for mercy. He could bear no more.