234 TRANSACTIONS OF THE ROYAL CANADIAN INSTITUTE |VOL. XI 
When a solution of double the strength was used, that is 1.0%, 
results were obtained which differed only in degree from those already 
described. The pits were larger, the beaks were shorter. The ill- 
defined figures mentioned in the previous paragraph were not observed, 
but each pit was surrounded by a shallow depression in which it seemed 
to have been developed (Plate XXVI, fig. 1). A curious feature noted 
here was that the beaks of two adjoining pits had become united, form- 
ing a connecting tube (Plate XXVI, fig. 2). It was noted also that the 
pits were not evenly distributed, the surface of the crystal being in some 
places closely covered, and in others comparatively free. The signifi- 
cance of this phenomenon, which has been frequently referred to by 
previous investigators, and which will be more thoroughly discussed 
on a later page, forms the basis of one of the main deductions of this 
paper. 
Stronger solutions gave larger, clearer pits and still shorter beaks. 
When 2% had been reached the pits were still very minute, and those 
on one side appeared to differ from those on the other in their rhombic 
outline, being more nearly lozenge-shaped. Distorted pits, enclosed by 
four non-parallel sides, two of which were distinctly longer than the 
others, were frequently seen. 
In consequence of the fact that, with colemanite, hydrochloric acid 
acts much less vigorously than acetic acid, the action of the former 
was more readily controlled and the results were correspondingly more 
satisfactory. It was found that a 1% solution gave pits which were 
much more primitive than those in the experiment previously des- 
cribed, in which a solution of acetic acid of half the strength was used, 
and there was the advantage that the pits were somewhat larger. Under 
these conditions there were produced numerous small, shallow depres- 
sions, whose sloping sides lacked the definiteness of figure faces. In 
most cases the depth was greater in one part, and set within was a clearly 
defined pit. (Plate XXVI, fig. 3). Weshall see that a similar primitive 
form was met with in the investigation of the figures on diopside. 
At this point, use was made of the method of exposing the crystal 
to the intermittent action of the same corrosive. After the first ex- 
posure to a 2% solution the surface was found to be covered with shallow, 
lozenge-shaped, asymmetric pits, set close together in parallel arrange- 
ment (Plate X XVI, fig. 4). There were no beaks. The pits observed 
after a second exposure had steeper sides (Plate X XVI, fig. 5). Some of 
these may have been the result of further development of the previous 
forms, but a few at least were new figures growing upon the sloping 
sides of the earlier ones. While further action resulted in the dissolving 
away of the etched surface in most cases, it was observed that here 
