Skey. — On the Cause of the Deposition of Camphor towards Lif/ht, 411 



hydrated to an equal extent with the salt which is separated thereby. It is 

 just probable, too, that such a salt must be in a crystalHzed form. 



2. That in all those cases where substances other than the salt of which 

 such solution is made are nuclear thereto, they act for this in an indirect 

 manner, the first step being a removal of water from such solution, and this 

 causes a portion of salt to separate — to form in its turn a nucleus capable 

 of acting directly on the solution. Nuclear action is therefore, in these 

 cases, always a result of secondary action. 



Akt. LXIV. — On the Cause of the Deposition of Camphor towards Light. 

 By William Skey, Analyst to the Geological Survey Department. 

 [Read before the Wellington Philosophical Society, 21st February, 1880.] 

 It has often been observed that when camphor has long been kept in a 

 glass bottle which is not evenly exposed to light, it detaches in part from 

 the bulk to encrust with crystals that side of the bottle which is " most 

 exposed to light." This partiahty of camphor for the more illuminated 

 surface is ascribed, as I take it, to an effect of light as an etherial undula- 

 tion distinct from that of heat possibly electrical. 



However, a few experiments which I made in this matter, show very 

 clearly that sublimation and condensation (as produced by heat and cold 

 respectively) are the sole cause of this kind of deposition. The whole matter 

 turns upon the diathermacy of the glass of the bottle used : though exposed 

 to hght most, it warms but slowly and up to but a httle way in the thermo- 

 metric scale. The camphor, however, absorbs the heat thus transmitted by 

 the glass, and the vapours formed thereby condense thereon, but for them 

 to select that side "most exposed to light" it is necessary that there be 

 ujjon or near to the other (the fm'ther side) some body absorbent of heat, so 

 that by its conduction therefrom, via the air, to this side, its temperature 

 may be raised to a higher degree than that of the other side, a circumstance 

 of course always obtaining in those cases where camphor is deposited 

 towards Ught. If no such kind of back-ground is present the camphor 

 deposits most upon that side of the bottle which is the furthest away from 

 light. 



In all probability the indications of weather got, or supposed to be got, 

 by the use of " camphor storm-glasses," are also produced not by electrical 

 or actinic action, or by light and heat in conjunction, as Dr. Parrion 

 suggests, but by variation of temperature only. 



