NOTES BY THE EDITOR. IX 



The lime light has recently been introduced into lighthouses, 

 and from its size bids fair to rival even the electric light for 

 some purposes. The light is white, and, according to the late 

 Prof. Faraday, very easily managed, it being necessary simply to 

 supply the oxygen and hydrogen gases which are directed against 

 the lime ; in Faraday's words, it is like the light of a planet, where- 

 as the electric light is like that of a star. The electric light, how- 



<j O ' 



ever, the brightest, has also been brought to the notice of the sci- 

 entific world by the magnificent electro-magnetic machines of 

 Wilde and Wheatstone; it rivals the light of the sun, and cannot 

 be looked at with the eyes unprotected. This has been applied to 

 lighthouses on the coasts of France, giving a light which can be 

 seen thirty miles at sea, and able to penetrate a dense fog. With 

 Foucaulfs regulator, which, by a system of clock-work driven by 

 the electric force, regulates the upward and downward move- 

 ments of the charcoal points as they are consumed, and also keep& 

 them in the focus of the lens, there seems nothing wanting to ren- 

 der this s}'Stem the most advantageous for lighthouses, and to 

 secure for it a general adoption for this purpose. 



The Holtz electrical machine has been variously modified by 

 practical physicists, until it now presents the simplest, cheapest, 

 most convenient, most powerful, and most reliable form of appara- 

 tus for the generation of frictional electricity. 



A discovery of very great importance to iron manufacturers is 

 described on pp. 173-4, namely : a method of detecting faults in 

 iron forgings by examination with a magnetic needle. Wherever 

 a flaw exists in the iron, as proved by many experiments in Eng- 

 land, it ceases to be one regular magnet, and the needle at once 

 departs from its normal position and assumes a new direction at 

 the place of the fault. This mode of testing detects the change 

 called crystallization, so important to be known in the matter of 

 railroad axles. 



Chemistry during the past year has been eminently progressive, 

 especially in the investigation of carbon compounds applicable in 

 the arts ; in fact the chemistry of carbon forms the predominating 

 study of the present age. It is evident that the atomic theory of 

 Dal ton, which has been of signal service in chemical progress, 

 must now be abandoned or fundamentally changed. Sir Ben- 

 jamin Brodie has recently laid before the scientific world a calculus 

 of chemical operations, in which the first systematic attempt is made 

 to express the constitution of chemical compounds by a method in 

 which the idea of an atom has no place. His starting-point is the 



