242 ANNUAL OF SCIENTIFIC DISCOVERY. 



directly into the alloy while in fusion, in which case the zinc is burned off, 

 and forms no combination with the fused metal. 



The following are conclusions arrived at by M. Bobierre, as the result of 

 his experiments, respecting the durability of copper-sheathing : 



1. When unalloyed copper is employed, the presence of arsenic appears 

 to hasten its destruction. 



2. All bronzes which appear to have stood well contained from four 

 and one-half to five and one-half per cent, of tin, that quantity being 

 necessary to form a homogeneous alloy. When the percentage of tin is 

 only 2.5 to 3.5, which is very frequently the case, no definite alloy is pro- 

 duced, and the mass is of unequal composition, and, being unequally acted 

 upon, is soon destroyed. 



3. When impure copper is employed, the alloy is never homogeneous, 

 and is unequally acted upon in consequence. We thus see that the so 

 frequent destruction of the sffeathing of copper-bottomed vessels arises 

 from the tendency to use inferior brittle copper, and, by diminishing the 

 proportion of tin, to economize the difference between the price of that 

 metal and copper, at the same time that the cost of rolling is also less, in 

 consequence of the greater softness of the poor alloy. 



Bobierre thinks that the addition of a very small portion of zinc very 

 much improves the bronze, by producing a more perfect and uniform dis- 

 tribution of the positive metals, and consequently a much more definite 

 alloy. Comptes Rend its. 



OBSERVATIONS, ECONOMICAL AND SANATORY, ON THE EMPLOYMENT 

 OF CHEMICAL LIGHT FOR ARTIFICIAL ILLUMINATION. 



The following paper has been read at the Royal Institution, London, by 

 Dr. E. Frankland : 



There are two principal sources of artificial light, viz., electricity and 

 the chemical force ; the latter, however, has been, and still is, the only 

 practical source of artificial light. Although light can be thus obtained by 

 the chemical action of substances belonging to all three kingdoms, yet 

 closer observations demonstrate that the illuminating effect from animal 

 and mineral bodies is primarily derived from the vegetable kingdom ; 

 every plant being an apparatus for the absorption and concentration of 

 light and heat from the solar rays, and for the retention of those forces 

 during its passage through the subsequent stages in the formation of vege- 

 table fuel. Until the commencement of the present century, artificial 

 light was derived almost exclusively from the animal kingdom ; but the 

 great economy attending its immediate production from our vast stores of 

 vegetable fuel is becoming more and more apparent, and in fact is so 

 generally admitted as to render more than a mere allusion to it, and a 

 glance at the following table, unnecessary. 



