GEOLOGY OF CAPE BRETON.—-GILPIN. 215 
recesses by the waves and ice. In the woods, from a distance, 
it recalls the tented homes of an army, or broods like a dis- 
mantled castle over some quiet valley. 
Soft and friable the untiring finger of time plays many a rude 
prank with it, and the malice of the destroyer of all things even 
follows it below ground. Subterranean streams wear it away, 
and with equal power remove the adjoining marls and shales, 
until the cover of a hidden pool falls in a crash. The inborne 
earth is soon coated with grass and shrubbery, and these funnel- 
shaped depressions mark the passage of the gypsum beds when 
no outcrop is visible. 
Thanks to the help of the microscope, and to our knowledge 
of the labors of marine insects the course of the formation of the 
limestones frequently associated with the gypsums can be readily 
followed. Weare, however, at a loss to account in an equally 
satisfactory manner for the growth of the gypsum masses. No 
branching coral, or mild bicarbonate formed this mineral, one 
half of which is the strongest and most deadly of acids. We can 
now perhaps imagine that some faulting of the rocks poured out 
springs carrying free sulphuric acid, this meeting limestone would 
lead to the formation of gypsum. Other scientists account for 
its formation by the slow process of concentration and evapora- 
tion of inland seas. Certainly it is frequently accompanied by 
salts of magnesia, and of sodium, etc., more or less pronounced 
ingredients of the ocean. Interesting as this question is, I could 
not attempt to do justice to Cape Breton if I were to discuss it 
now. 
The gypsum occurs in every variety of color. The prevailing 
color is white, which is shaded into blue, but it is noticed red, 
black and blue, and occasionally green. The anbrydrite variety 
is white, pale blue and gray. Both varieties occur massive, crys- 
talline, and granular. The tabular translucent crystals, known 
as selenite, are frequently taken for mica. The beds of gypsum 
vary in thickness up to one hundred and fifty feet, and proxim- 
ately continuous, extend often for miles. The minerals is 
frequently found in crystals and veins in marls, shales, and 
