210 DAVIES, ON CRYSTALLIZATION AND THE MICROSCOPE, 
to start the crystallization afresh, even a slight breath suf- 
ficing, reuders this explanation, I think, trustworthy. 
We will now consider the influence of the magnesia in the 
double salt : 
Photograph No. | shows crystals of sulphate of copper im 
prisms, magnified 200 diameters, this being the received form 
of the salt. 
Photograph No. 2 illustrates the result of adding a small 
quantity of magnesia. A considerable influence is exerted 
over the copper; but there is only slight action upon the 
“yadii,’’? their circular and broken forms not being of suffi- 
ciently decided appearance to call to mind their resemblance 
to a flower. Perhaps it might humorously be described as a 
flower whose leaves were slowly unfolding. 
Photograph No. 2. 
Photograph No. 3.—Here the full complement of mag- 
nesia has been added, the flower is in perfection, and the 
crystals in full form and beauty. This slde has been mounted 
three years, and has not undergone any visible change. 
When the double salt is crystallized upon a smooth sur- 
face it seldom shows itself in any form except the circular 
one, resembling flowers in greater or less degree; but in one 
or two instances I had noticed imperfect rhombs at the 
edges of the slides. I therefore made a saturated solution 
