SCIENCE NOTES.

Digger (Invercargill RSA), Issue 32, 22 October 1920, Page 13

SCIENCE NOTES.

' CABLE CONSTRUCTION. Despite the great development. of wireless telegraphy, submarine cables are still being constructed, and with d.he great increase in commercial and journalistic messages are still regarded as a necesisary alternative to wirelesg, and by no means obsolete or likely to fall into disuse. In fact a new cable to the Far East irom Great Britain through the Mediterranean, involving a length of 7000 miles, is being laid section by section as ready, while the possibility of a new cable from Vancouver to Fanning Island is now being discussed. MAZOUT. Mazout is the narne given to the new fuel being tried in Frahce. It is described as "petroleum residue," which presumably is the coarser leavings after the hghter parts have been refined away. France produces, and believes in, mazout as a complete substitute for ooal on her main-line railways,,. and is being greatly encouraged by its many advanfages. Already 400 engines on one French railvvav have been converted to burn the new tuel It gives forth no smoke or sparks. It requires less laboui', for the stokiiig is done by turti.'.g a tap. It will get up as oiuch steam in forty minutes as coal will in 180 minutes. It will run an express train at 60 miles an hour and drag 60 twentyton waggons on a long journey. MAP PROJECTORS. The United States Coast and Geodetic Surve-y has been devoting much attention of late to the subject of map projections, and has issued geveral interesting memoirs relating to the projections which have t een little used, together with specimen maps. The latest publication of this sort is a new outline base map of the United States on the Lambert zenithal equal-area projection, scale 1 :7, 500, 000. This is t-he first map of this projection ever published by the- survey. Besides its useful property of equal area, the projection has smaller scale and direction errors than the polyconic projection map which has been so frequehtly used for political census, and miscellaneous gtatistical purposes. ELECTRICAL TURN INDICATOR. There has recently been introduced in German flying circles an instrument tnat indicates the difference in air speed bc tween the two wing tips, which is but an. other way of expressing the rapidity of turns. Two venturi tubes are used, one over each wing tip. Each venturi contains ihree resistance thermometers, one in the throat, one in the entrance section, and one in the exit- section. The temperature one in the exit section. The temperature difference between the throat and the entrance and exit can thus be obtained for each venturi. By combining two instruments differentially, the differences in temperature between the two throats can be measures. This temperature difference will depend on theratte of turn. ing. It is claimed that the electrical record. er has very little lag. INTENSITY OF WIRELESS SIGNALS. A method of measuring and comparing the intensities of signals received by a radio station has been worked aut in France with good results. This method which can be employed only for undamped waves, essentially consists in comparing the intensities of receptlon of the signal and of the sound produced by ( a local source of oscillations, of the same frequency and form, constituted by an ordinary heterodyne. By modifying the intensity of the aci^on of the auxiliary oscillation-generating device upon, say, the antenna, a rough equalisation is first obtained, afterwards, by manoeuvring convenient shunts to the telephone an ahsolute equalty of intensities is obtained. The ration of intensities is proportional to the shunt resistances. Moreover, by inserting a thermo-galvanometer in the antenna the absolute value of the intensity of the auxiliary signals can be obtained. The error in the practical use of this method is from 5 to 10 per cent-