Selenium in Commercial Sulphuric Acid. 313 



more than 100 miles across, should have been covered with a 

 sheet of ice so thick as to bury mountain ranges more than 

 1000 feet in height, almost at the sea-shore. But all our 

 difficulties disappear when we reflect that the seas around 

 Scotland, owing to their shallowness, were, during the 

 glacial period, blocked up with solid ice. Scotland, Scandi- 

 navia, and the North Sea would form one immense table- 

 land of ice from 1000 to 2000 feet above sea-level. This 

 tableland would terminate in the deep water of the Atlantic 

 by a perpendicular wall of ice, extending probably from the 

 west of Ireland away in the direction of Iceland. From this 

 barrier icebergs would be continually breaking off, rivalling 

 in magnitude those that are now to be met with in the 

 Antarctic Seas." * 



XXX. 0)1 the Occurrence of Selenium in Commercial Sulphuric 

 Acid, and its Action on Mineral Hydro-Carlon Oils. 

 By James C. Hamiltoit, Esq. 



(Read 21st February 1883.) 



Before entering into the subject of the action of selenium 

 on mineral hydro-carbon oils, it may be not uninteresting to 

 some of the members present, if I were to give a short sketch 

 of the production and manufacture of these oils, and the 

 manner in which selenium would be liable to affect them. 



The shale from which the oil is produced is brought 

 directly from the pits or mines where it is found to the 

 retorts. In this state the sizes of the pieces of shale are very 

 unequal ; and to make them of a comparatively equal size, 

 and also to enable the oil vapours to escape more easily, the 

 shale is put through w^hat is known as the " Ireaker.'' 



From the breaker the shale is put into the retorts. Various 

 kinds of retorts are used, the three commonest forms being 

 the Henderson Patent, the Vertical, and the Young & Beilby, 

 all possessing attributes suitable to the different kinds of 

 shale. In all these retorts, steam, either superheated or soft, 



* " Climate and Time," p. 452. 



