236 Scientific Intelligence. 



8. Expansion of Melted Quartz. — The new uses of melted 

 quartz, or more exactly amorphous silica, make the determination 

 of its physical properties of importance. Vessels made from 

 amorphous silica have the remarkable property of acting like 

 metals when subjected to heat. After being heated to a red 

 heat they can be plunged into cold water without injury. L. 

 Holborn and F. Henning have measured the expansion coefficient 

 of this substance and find it to be 0*00000054. — Ann. der Physik., 

 No. 2, 1903. j. t. 



9. Purification of Prinking Water by Ozone. — The use of ozon- 

 ized air for this purpose is attracting attention. 



The East London Water Company has been carrying out trials 

 at Lea Bridge with one method and appear to be fairly success- 

 ful. Prof. Van't Hoff lately gave some details of the Vosmaer- 

 Lebret process. The ozonizer in this process does not use glass 

 and the silent discharge takes place between the walls of metallic 

 tubes. An electromotive force of 10,000 volts is employed. A 

 large portion of organic matter and of the colonies of bacteria 

 were removed by the process. — Nature, Jan. 1, 1903. j. t. 



10. A disturbance free Torsion Magnetometer. — The present use 

 of the earth for returns by the electric tramways makes the care- 

 fully perfected methods of Gaus and Weber almost useless. F. 

 Kohlrausch and L. Holborn describe a new instrument which 

 overcomes many of the difficulties which have arisen in the use of 

 old methods. A complete description of the instrument is given. 

 The position of rest of the suspended portion remains for months 

 with a change of barely one scale division ; and the instrument 

 is not affected by the sudden changes due to the electric roads in 

 the neighborhood of the Reichanstalt. — Ann. der Physik., No. 2, 

 1903. ' j. t. 



11. Fatal effect of Electric Currents of low Potential. — It has 

 been often maintained that a potential below a thousand volts is 

 not dangerous to human life. Numerous casualties have shown 

 the fallacy of this belief. The current strength is just as import- 

 ant a factor as the electromotive force. There is no question 

 that a potential of 500 volts with a strength of current such as is 

 employed on the third rail system in our cities is deadly, when 

 good contacts are obtained. A fatal accident occurred at the. 

 Fulham public baths in England, on Dec. 28, 1902. Two bathers 

 were killed by standing up in the bath and grasping an electric 

 conductor which ran alongside the baths. The voltage was only 

 170. Very good contact was obtained. — Nature, Jan. 8, 1903. 



. J. T. 



12. Velocity of X- Pays. — Mon. M. R. BLONDLOTby an ingeni- 

 ous method has measured this velocity in air and finds it to be 

 the velocity of light. The principle of his method consists in 

 employing the well known property of the X-rays in facilitating 

 the spark discharge. Electric waves along wires were produced 

 and at definite distances it was found that the rays increased the 

 amplitude of these waves. A consideration of wave lengths and 



