MECHANICS. 81 



known. Many other methods of physico-chemical research are being 

 successfully prosecuted at the present day, but it would go beyond the 

 bounds of this summary even to enumerate these. 



The concordant results obtained by these widely differing methods 

 show that those chemists who have devoted themselves, frequently 

 amid the ridicule of their more practical brethren, to ascertaining by 

 purely chemical methods the constitution of compounds, have not 

 laboured in vain. But the future doubtless belongs to physical 

 chemistry. 



In connection with the rectification of the atomic weights it may 

 be mentioned that a so-called natural system of the elements has been 

 introduced by Mendelejeff (1869), in which the properties of the ele- 

 ments appear as a periodic function of their atomic weights. By the 

 aid of this system it has been possible to predict the properties and 

 atomic weights of undiscovered elements, and in the case of known 

 elements so determine many atomic weights which had not been fixed 

 by any of the usual methods. Several of these predictions have been 

 verified in a remarkable manner. A periodicity in the atomic 

 weights of elements belonging to the same class had been pointed out 

 by Newlands about four years before the publication of MendelejefFs 

 memoir. 



In mechanical science the progress has not been less 

 remarkable than in other branches. Indeed to the im- 

 provements in mechanics we owe no small part of our 

 advance in practical civilisation, and of the increase of 

 our national prosperity during the last fifty years. 



This immense development of mechanical science 

 has been to a great extent a consequence of the new 

 processes which have been adopted in the manufacture of 

 iron, for the following data with reference to which I am 

 mainly indebted to Captain Douglas Galton and Mr. 

 Rendel. About 1830, Neilson introduced the Hot Blast 

 in the smelting of iron. At first a temperature of 600 or 

 700 Fahrenheit was obtained, but Cowper subsequently 

 applied Siemens' regenerative furnace for heating the 

 blast, chiefly by means of fumes from the black furnace, 



G 



