'''biolecular coalescence/^ etc. 231 



3rd, with 1 equivalent of oxalate to 4 of chloride. 



The plugs, removed simultaneously at the end of six days, 

 were found very differently charged with deposit. In all, the 

 precipitate Avas confined to the upper (oxalic) half of the 

 plug, leaving the lower (calcic) half quite clear. 



In No. 1 the deposit was divided into two strata; the 

 lower, a little less than half, denser ; the upper, rather more 

 than half, more scanty. 



In No. 2 a narrow line of excessive density ran along the 

 lowest part of the deposit, leaving the portion above rather 

 less dense than the upper part of No. 1. 



In No. 3 a very dense deposit filled the ujjper half of the 

 plug, except at a very thin line in contact with the oxalic 

 solution. In all three cases the denser tract of the plug con- 

 tained coalescence-forms with octohedra. On the side of the 

 oxalate were large wheatsheaves, bundles of crystalline plates 

 looking like ^jackets of docketed letters tied tightly round the 

 middle, and octohedra of moderate size with much-broken 

 angles (PL XVI, fig. 6). 



On the calcic side the wheatsheaves were replaced by 

 smaller, rounded, homogeneous dumb-bells of great beauty ; 

 the octohedra Avere much larger, flattened in the direction of 

 their jjerpendicular axes, and much drawn out at their angles, 

 their internal structure being at the same time disturbed. 

 The upper scantier layer of deposit contained in all three 

 cases the same forms — a series running from granular exuda- 

 tions of crystalline matter to tolerably perfect octohedra, with- 

 out any associated coalescence forms. In the lower half of 

 the plug, just below the dense line, was a shallow layer of 

 exquisitely perfect small octohedra, with their three axes 

 nearly equal. BeloAV this layer the plug contained nothing. 

 Comparing the plugs in other respects, it was noted that the 

 coalescence-forms were most abundant in the broad tract of 

 No. 3, most perfect in the thin dense line of No. 2, where the 

 wheatsheaves were so luxuriant as to form spheres of radiant 

 crystal, and the dumb-bells were compacted into lustrous 

 spherical beads. 



4. Lime water and oxalic acid were now used in the beaker 

 and tubes respectively; but the oxalic acid was evidently 

 much more diffusible than the lime, and the plugs were filled 

 with a slight deposit, corresponding in the main to the upper 

 scantier deposit of the foregoing experiments, and contained 

 only a few tables and bundles of plates at the very lowest 

 point. When equivalents were used, all the forms were 

 small, and the tablets were little oval-pointed lozenges. When 

 two equivalents of oxalic acid and one of lime were used, the 



