28 ADIPOCIRE 



Now, if any substance capable of undergoing chemical change be exposed to this 

 spectrum, the result will bo found to be such as is represented in the accompanying 

 drawing, ./fy. 15. Over the space upon which the greatest amount of light falls, i.e., 

 the region of the yellow and orange rays L, no chemical change is effected : by pro- 

 longed action a slight change is brought about whore the red ray falls, r, but from 

 the mean green ray g up to the point /, a certain amount of chemical action is 

 maintained ; the maximum of action being in the blue and violet rays A. Thus the 

 curved line (fig. 14) from e to /represents the extent and degree of chemical power 

 as manifested in the solar spectrum. Two maxima aro marked A A, differing widely, 

 however, in their degree. 



Here, as in Berard's experiments, we see that whore the light is the strongest, there 

 is no chemical action, and that as the luminous power diminishes the chemical force 

 is more decidedly manifested. 



Again, we find that if we take a piece of yellow glass, stained with oxide of silver, 

 we have a medium which entirely prevents the permeation of the chemical rays, 

 though it obstructs no Light. But, if a very dark blue glass is taken, we find that 

 ninety per cent, of the luminous rays are obstructed, while the chemical rays permeate 

 it most freely. Numerous experiments of an analogous character appear to prove 

 that the chemical and luminous powers of the sunbeam are balanced against each other 

 (see Hunt's ' ^Researches on Light '), that they are indeed antagonistic principles or 

 powers. That there are three very distinct sets of phenomena, every one admits. 



LIGHT (luminous power"), to which belongs the phenomena of vision and the produc- 

 tion of colour. 



HEAT (calorific power), the function of which appears to be the determining the 

 physical condition of all matter, as regards its solid, fluid, or gaseous condition. 



ACTINISM (chemical power), to which all the phenomena of photography are due, and 

 many of the more remarkable changes observed in the vegetable kingdom. 



ACTINO-CHKMISTRY was a term first applied by Sir John Herschel, and has been 

 generally adopted to indicate the phenomena of chemical change by the action of the 

 solar rays. Actinism was first proposed to express the chemical principle of the sun- 

 beam by the Editor of this Dictionary at the meeting of the British Association 

 at York. 



ACTING GRAPH. A name given to an instrument for recording the variations 

 in the chemical (actinic) power of the solar beams. The name signifies ray writer. 



ACTINOIiITE. A variety of Hornblende See HORNBLENDE. 



ACTIlTOMEiTER. (Ray measurer.) The name of various forms of instuments, 

 the objects of which are to measure the direct heat radiations from the sun. The 

 term has also been applied to instruments employed to measure the varying inten- 

 sities of Light. 



ADAMANTINE SPAR. An old name for Corundum. See CORUNDUM. 



ADAMITE. A native hydrous arsenate of zinc, occurring in the silver-mines of 

 Chanarcillo in Chili, and in the Dep. du Var, France. 



ADAM'S NEEDIiE, A name commonly given to the Yucca gloriosa, a plant 

 belonging to the Liliacets or Lily-order, the fibres of which have been used ia tho 

 manufacture of paper. 



ADANSONIA DXCITATA. The Baobab tree, a native of Western Africa. 

 It yields a fibre which has lately been used in paper-making. 



ADDITION'S. Such articles as are added to the fermenting wash of the distiller, 

 were of old distinguished by this trivial name. 



ADHESION 1 (sticking together). The union of two surfaces. With the pheno- 

 mena which are dependent upon bringing two surfaces so closely together that the 

 influence of cohesion is exerted, we have not to deal. In arts and manufactures, 

 adhesion is effected by interposing between the surfaces to be united some body 

 possessing peculiar properties, such as gum, plaster, resin, marine or ordinary glue, 

 and various kinds of cement. Adhesion should be restricted to mean, sticking together 

 by means of some interposed substance; cohesion, the state of union effected by 

 natural attraction. 



Not only is adhesion exhibited in works of art or manufacture ; we find it very 

 strikingly displayed in nature. Fragments of rocks which have been shattered by con- 

 vulsion aro found to be cemented together by silica, lime, oxide of iron, and the 

 like ; and broken parts of mineral lodes are frequently reunited by the earthy minerals. 



ADXPIC ACID. C' 2 H' 0". (C 6 H 10 O 4 .) One of the fixed fatty acids pro- 

 duced by the action of nitric acid on oleic acid, suet, spermaceti, and other fatty 

 bodies. See Watts's ' Dictionary of Chemistry.' 



ADIPOCIRE. From adcps, fat ; cera, wax. (Adipocire, Fr. ; Fettwachs, Ger.) 

 The fatty matter supposed to be generated in dead bodies buried under peculiar 

 circumstances. It is chiefly margarate of ammonia, In 1786 and.. 178 7, when, the 



