THE VARIATION OF ANGLES OBSERVED IN CRYSTALS. 
Such speculations are, however, at present beyond the test of experinient, neither 
is it possible to say what paiticular vicinal faces correspond to a ceidain concentrati(.)n 
of tlie solution until more is known concerning the nature ol these layers ot solution 
immediately adjacent to the crystal. In particidar, it will l)e necessary t(^ make 
accurate determinations of the change of volume })i’oduced by dissolving the crystals. 
It is sufficient to p(.)int out that the wider spacing of the material l)efore it 
solidifies is a reason why the crystallising sid^stance shoidd descend u})on tlie gr(jwing 
crystal in a shower which is not very dense ; and this again is a reason why the 
growth should take place along vicinal })lanes, and not along planes witli simple 
indices. That the growth does take place along vicinal planes has Ijeen aljundantly 
proved, at any rate for alum, in the preceding })ages ; that the spacing is very much 
wider in the liquid than in the crystal has been proved l)y showing tliat the liquid 
about to crystallise is scarcely more than saturated. 
Very slight variations in the concentration of the solution would proljalfiy 
correspond to considerable difierences in the vicinal planes })roduced. 
The observations recorded above raise many interesting questions ; ljut I have 
thought it better to confine myself in this })aper maiidy to observed facts, and to 
reserve further speculation for another occasion, hoping in the meantime that the 
eiupiiry into the nature of the licpiid in contact with a growing crystal, wliicli is liei'e 
opened, will be pursued by others in a more systematic and exhaustive manner. 
Note .—A brief statement of some of the results recorded in Part 1. (pp. 45'J-4b2) 
was published in the Heport of the British Association for 1894, p, G54. 
In the latter part of the research I have received useful lielp from my assistant, 
Mr. PiCHARD GitAiiAM, by whom many of the observations in Part II. were made. 
PIli.?!ENTED 
1 8 DEC. 1903 
3x2 
