D. CHEMISTRY AND METALLURGY. 193 



D. CHEMISTRY AND METALLURGY. 



CHEMICAL ACTION OF SOLAR EAYS. 



Henry E. Roscoe states that although his method of 

 measuring the varying intensity of the chemically active 

 rays as affecting chloride of silver paper has been the 

 means of pointing out many important facts, yet it has not 

 been introduced as a regular portion of the work of meteor- 

 ological observatories ; until which is done we can not hope 

 to obtain any thing like a complete knowledge of the laws 

 of distribution of the chemical rays over the earth's sur- 

 face. This neglect of Roscoe's method is, in part at least, 

 due to the labor of observing. He has, therefore, advised a 

 modification of the instrument described by him in 1865, 

 and as thus modified the constant sensitive paper is exposed 

 to the action of total daylight at given intervals, say at every 

 hour during the day, by a self-acting arrangement for ac- 

 curately noting the times. These hourly records are then 

 read off in the evening by the observer. Many mechanical 

 difficulties have been overcome through the skill of Mr. 

 Jordan, of Manchester, and the instruments, as described by 

 Roscoe in the last volume of the "Transactions of the Royal 

 Society of London," are said to give complete satisfaction. 

 In order to read off the intensities of recorded photographic 

 images, a standard series of graduated tints is provided. 

 Special directions are given for the preparation of the sensi- 

 tive paper. The correction due to the reflection and absorp- 

 tion of the glass cover is also investigated ; and the compar- 

 ison of observations made by hand, and by the self-record- 

 ing instrument, over twenty days with the two methods, close- 

 ly agree. PhilosopluQal Transactions^ London^ 1875, 655. 



OCCLUDED HYDROGEN IN SO-CALLED EXPLOSIVE ANTIMONY. 



The presence of a considerable amount of chloride of anti- 

 mony was demonstrated several years ago, by Professor 

 Bottger, in the so-called explosive antimony formed on the 

 negative pole, consisting of fine platinum wires, the positive 

 one being of massive antimony, when the current of a single 



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