115 GYPSUM. 
amount of time, nor the other surrounding conditions are available ; 
but if I can show you that when iron sulphate and free sulphuric 
acid act upon calcium carbonate to yield Gypsum, and that the other 
product is iron bi-carbonate, which, when exposed to the air, yields 
red iron oxide, I think you will all be prepared to admit that, what- 
ever credence you may care to give to other speculations, this, 
as shewn by experiment, is an established fact. 
Here is a small beaker in which I placed powdered limestone, 
I added iron sulphate slightly acidulated with sulphuric acid and 
digested for a time. The red oxide of iron is readily noticeable, some 
iron carbonate is also present, because sufficient time has not elapsed 
to ensure complete oxidation. On examining the deposit under the 
microscope crystals of “Selenite,” crystallised Gypsum, are observed, 
identical in form with those occurring in nature in the Lias and 
Oxford clays, &e. 
These are the facts and speculations to which I have endeavoured 
to draw your attention to-night. I must express my regret that I 
have been unable to present them to you in a more pleasing form, 
but, if I have been able to put the broad facts before you in such a 
shape as will enable anyone of you to follow them up, [ shall be 
satisfied. 
The question is of much interest and may give the key to the 
mode of deposition of the beds, beginning with the Keuper after the 
Bunter. These are free from, or mainly free from, fossils. Iron 
sulphate and free sulphoric acid are not constituents of a nidus in 
which plants and animals could live, prosper and be preserved. 
