SCIENCE NOTES.

Otago Witness, Issue 3662, 20 May 1924, Page 69

SCIENCE NOTES.

A CHEAP PARAFFIN NIGHT-LIGHT. What may be called the night-light typo of paraffin lamp has now become common, largely owing to the economies forced upon us by tne war. tramps ol this kind are freely used in places where only a dim light is required, even by householders who employ gas or electric lamps for ordinary lighting. A very simple and cheap lamp of this type, known as the “Tweenie,” lias recently made its advent. It consists of a tin saucer, provided with a handle, upon which is mounted a hollow cone ol tin filled with cotton-wick. The apex of the cone is cut down to a point that leaves an aperture large enough for the wick, which is adjusted by means of a pin through a small hole in the side. At the bottom, the oone is cut away slightly at each side. This lamp is not filled in the ordinary way—in fact, there is no filling-hole, but paraffin is poured into the saucer, and runs into the cone until the wick is saturated, when the lamp can be lit, and will bum foir about 12 hours. The “ Tweenie ” lamp is painted in various colours, and, being so simple, it can be sold at a very low price. A NOVEL FORM OF DOUBLE SAUCEPAN. During the last few years increasing attention has been rightly paid to the invention oi new domestic appliances and the improvement of those already in use. Among other household aids that have recently been placed on the market is a double saucepewi which presents several novel features. The outer portion is mad° of stout tin-plate, and is provided with a beaded rim. Resting upon the rim, and separated from the outer pan by a space of about three-quarters of an inch all round, is a cage or frame with three legs connected to a perforated disc. This frame carries an inner pan or container, which fits easily, and is furnished with a handle for lifting it out. Being made ol glazed earthenware, the container is ideal for cooking purposes, and is easily cleaned. It is exceedingly durable, and in case of accident a new one can be obtained at a reasonable cost. This inner container has also the advantage that when the cooking is completed it can be lifted out, and placed direct upon the table, with a table-napkin wrapped round it to keep the contents hot. .During the process of cooking the cook can remove the lid a't any time, observe the height of the water in the outer pan, and ado to it, if necessary, without interrupting the culinary operation. With ordinary care the food in the container will neither boil over nor burn, nor will it stick to the pan, although left untended for a considerable time. After use the various parts of the saucepan can be readily dried, thus preventing corrosion of the outer pan, and adding to its life. The essential part of this helpful domestic utensil-—namely, the container —may be had from the manufacturer in three sizes -—of one pint, two pints, and three pints capacity,—and as the outer pans, the cages, and the containers can be purchased separately, any part of the apparatus coming to grief can be easily re newed, while the housewife who already possesses a saucepan of suitable size can readily obtain a cage and a container to fit. THE SIGNIFICANCE OF CRACKS. In his Memorandum to the Manchester Steam Users’ Association, recently published, Mr C. E. Stromeyer describes experiences of this Association in respect to cracks in the dished end plates of boilers. These cracks occur in the angle at the flanged circumference of the plates, but in numerous instances the crack does not spread once it is formed. Mr Stromeyer observes that a test pressure applied to a steel boiler has never yet produced cracks at the roots of the flanges of tlie end plates, and that the cracks must accordingly be attributed to fatigue. It may be noted that these observations afford a striking testimony as to the validity of the theory that, at any rate in the case of tough metals, secondary stresses, when non-alternating, are never responsible for a catastrophe. Mr Stromeyer states the experience of years leads to the view that when cracks do appear in the roots of the flanges after some years’ working, they relieve the stresses which are, of course, of a strictly “secondary” character. It appears, therefore, in these cases, at any rate, the over-load due to excessive secondary stresses is passed on to the less stressed positions, sometimes with, and sometimes without, any crack being- produced. In the former case it is, of course, a matter of prudence to watch the crack, but the experiences stated indicate that there is no immediate danger. An accurate calculation of tlie stresses in a dished end would be a task of some difficulty, jas the structure is indeterminate to a very marked degree. Equilibrium is in fact possible, with a practically infinite number of “boundary conditions.” If, however, the latter were assumed, it would seem that the problem of the stress distribution ought to be soluble in terms of Legendre’s coefficients, but the expansions might no doubt be troublesome to evaluate.—Engineering. WATER PIPES THAT DO NOT FREEZE. Among the many matters in connection with the housing question which have been brought to tlie attention of architects by housewives, is the demand for “waterpipes that do not freeze.” Such a demand appears at first sight extravagant, but in reality it is far from being so. It is apparently not known in Britain that this problem was solved long ago in America and Canada, and in a very simple, ingenious, and inexpensive way. In British

houses, as most householders know, the water-supply is turned on or off In each individual house by means of a stop-cock which is invariably placed outside the house. In the case of American and Canadian houses, the place of this stopcock is taken by an extremely simple and ingenious device known ns a “stop and waste” cock, which is always placed inside the house in a very accessible position. Without entering here into technical details, we need only say that this “stop and waste” cock is of such construction that whenever it is turned off, all waterpipes in the house leading fi-om the main are automatically and immediately drained, and are thus prevented from freezing. When the “stop and waste” cock is turned on, it admits a full supply of water to the house, precisely like the British stop-cock. It is absolutely “foolproof,” and is just as simple in operation as any common tap. While the “stop and waste” cock is always buried, so that it cannot freeze, it has a long handle firmly attached to it, which projects upwards through the floor, and by means of which it is turned oil or off. It is usually placed in the kitchen close to the sink, experience having shown that to bn .tlie most generally suitable position. Obviously, waterpipes in a house are most likely to freeze at night; consequently, in severe weather, the householder turns the cock off before going to bed, in absolute certainty that no frozen water-pipes will await him in the morning when he turns the cock on again. Why British architects have not, long ere this, insisted upon the adoption of this simple and inexpensive device, in addition to the outside stop cock, is a mystery. As matters stand at present, it is compulsory in Britain that there should be an outside stop-cock. This is usually placed in tho pavement in the street, and n key, which can never be found in an emergency, is required to turn it on or off. Hence, if a pipe bursts, hardly one householder in a hundred knows where or how to turn the water off; the great majority are compelled to stand helplessly by and witness the devastation caused by tlie flood of water until a plumber arrives. With the provision of an inside stop-cock, all danger of this would be obviated.