Beports and Proceedings — British Association. 421 



years, and this is no doubt very useful and instructive ; but if we are 

 to go forward in our scientific work we must not be satisfied with 

 the patient accumulation of details, or content to congratulate 

 ourselves upon the number of them which have been amassed. 

 I venture to think that it is more profitable to take our stand upon 

 the actual work of to-day, and from that tower of observation to 

 look forward to the future rather than backwards to the past; to 

 exclaim with the poet — 



" No, at noonday in the bustle of man's work-time 

 Greet the unseen with a cheer ! 

 Bid him forward." 



It would be interesting enough to trace the history of the artificial 

 reproduction of minerals, beginning with the famous experiment of 

 James Hall ; to follow the lines that led to the development of the 

 French School during the last half of the nineteenth century; to 

 dwell on the researches of Senarmont, Ebelmen, Daubree, and 

 Sainte-CIaire Deville ; to show how the increasing study of 

 petrography and the invention of the electric furnace have led to 

 renewed activity in the attempts to reproduce igneous rocks and the 

 rock-forming minerals ; to discuss the more modern experiments of 

 Fouque and Levy, Lagorio, Loevinson-Lessing, and Morozewicz ; or 

 to describe the manufacture of many an interesting mineral by 

 de Schulten and others who are actively prosecuting research of thi? 

 nature, including such sensational achievements as the production of 

 the ruby by Fremy and of the diamond by Moissan. 



Instead, however, of attempting a survey of all that has been done, 

 or even of all that is being done in the artificial reproduction of 

 minerals, let me adhere to the principle that I have laid down, and 

 discuss only a few of those researches, now being carried on, which 

 promise to be most fruitful because their methods and aims are 

 inspired by the discoveries and views of modern chemistry and 

 modern physics. 



Van 't Soff's Worh on the Salt Deposits. 



Among such researches the most remarkable are those conducted 

 by Professor van 't Hofi' and his pupils during the last eight years 

 upon the Stassfurt salt deposits. These deposits are of enormous 

 extent, more than 1,000 feet thick, and consist of fairly well-defined 

 layers of various sulphates and chlorides of sodium, magnesium, and 

 potassium, and their double salts and hydrates. It has long been 

 supposed that the minerals have been derived from the evaporation 

 of sea-water which contains in solution the chlorides of sodium, 

 magnesium, and potassium, with sulphate of magnesium and small 

 quantities of calcium salts ; and the general sequence of the minerals 

 is that of their solubility ; the less soluble sodium chloride crystallised 

 out first and is at the bottom, while the very soluble magnesium 

 chlorides, having been the last to crystallise, occupy the top of the 

 series. But the problem is by no means so simple as to be one of 

 mere solubility in water; the rock salt itself persists through the 

 whole series, and some of the associations are difficult to explain. 



