1870.] Physics. 563 



11. PHYSICS. 



Light. — A new substance possessing fluorescent properties in a 

 very high degree has been prepared by Professor A. H. Church 

 from the Cyclopia vogellii, one of the plants used by the African 

 Boers for tea. It possesses acid properties, and the discoverer calls 

 it cyclopic acid. Its action on fight is best seen when a crystal or 

 two of the new body is dropped into a solution of caustic soda and 

 viewed in sunlight. An intense greenish -yellow fluorescence is 

 perceived at first, but disappears in the course of some hours. 



A new artificial light which has recently been successfully ex- 

 perimented with, called the Philipp carbo-oxygen lamp, and its 

 recent trial at Cologne, was such as to win approval on every hand. 

 The light is generated by the combustion of a liquid chemical com- 

 pound in a current of oxygen, arrangements for the purpose being 

 constructed in a suitable lamp. The gas is derived from the 

 atmosphere either by chemical or mechanical means; the chemical 

 methods being to absorb the oxygen of the air with chloride of 

 copper (Mallett's method), or with manganate of potash (Tessie du 

 Mothay's method), while the mechanical mode is that of utilizing 

 the different degrees of solubility of nitrogen and oxygen in water 

 or other liquids. By compressing atmospheric air into receivers 

 filled with water, a portion of the nitrogen is taken up by the 

 water, while the oxygen remains insoluble in the water; the air 

 thus containing a goodly proportion of oxygen is forced into a 

 second reservoir of water, where a further amount of nitrogen is 

 absorbed, and after the operation has been repeated seven or eight 

 times, an atmosphere is obtained containing 97 per cent, of oxygen. 

 The nitrogen which has been separated is made use of in a well- 

 constructed apparatus as an auxiliary to the motive force. Expe- 

 riments have established the fact that a flame fed with air contain- 

 ing 53 per cent, of oxygen yields a light equal in brilliancy to that 

 obtained with pure oxygen, and with diluted oxygen of this kind 

 the Philipp flame has a brilliancy of 90 to 100 candles, or ten 

 times that of an ordinary gas jet. The light is of a bluish-white, 

 resembling very much that of electricity or burning magnesium. 

 The liquid employed consists of liquid hydrocarbons very rich in 

 carbon ; it costs but httle, burns economically, and can be em- 

 ployed only in this particular direction. The flame is made to 

 assume the form of a star, and any heating of the wick-holder 

 thereby prevented ; if of the size and power above mentioned, the 

 quantity of gas consumed is 5-J cubic feet per hour. As to the 

 lamp, no special attention is necessary beyond that of filling it with 

 liquid, as the wick is of a very durable nature, and needs no trim- 

 ming. 



