THE RECENT PROGRESS OF PHYSICAL SCIENCE. 741 



bly, if the truth were known, we should see that, in nine cases out of 

 ten, success depends as much upon good judgment and perseverance 

 as upon fertility of imagination. The labors of our great inventors 

 are not unappreciated, but I doubt whether we adequately realize the 

 enormous obligations under which we lie. It is no exaggeration to say 

 that the life of such a man as Siemens is spent in the public service ; 

 the advantages which he reaps for himself being as nothing in com- 

 parison with those which he confers upon the community at large. 



As an example of this it will be sufficient to mention one of the 

 most valuable achievenaents of his active life — his introduction, in 

 conjunction with his brother, of the regenerative gas-furnace, by 

 which an immense economy of fuel (estimated at millions of tons an- 

 nually) has been effected in the manufacture of steel and glass. The 

 nature of this economy is easily explained. AVhatever may be the 

 work to be done by the burning of fuel, a certain temperature is neces- 

 sary. For example, no amount of heat in the form of boiling water 

 would be of any avail for the fusion of steel. When the products of 

 conxbustion are cooled down to the point in question, the heat which 

 they still contain is useless as regards the purpose in view. The im- 

 portance of this consideration depends entirely upon the working tem- 

 perature. If the object be the evaporation of water or the warming 

 of a house, almost all the heat may be extracted from the fuel without 

 special arrangements. But it is otherwise when the temperature re- 

 quired is not much below that of combustion itself, for then the 

 escaping gases carry away with them the larger part of the whole heat 

 developed. It was to meet this difficulty that the regenerative-furnace 

 was devised. The products of combustion, before dismissal into the 

 chimney, are caused to pass through piles of loosely stacked fire-brick, 

 to which they give up their heat. After a time the fire-brick, upon 

 which the gases first impinge, becomes nearly as hot as the furnace 

 itself. By suitable valves the burned gases are then diverted through 

 another stack of brick-work, which they heat up in like manner, while 

 the heat stored i;p in the first stack is utilized to warm the unburned 

 gas and air on their way to the furnace. In this way almost all the 

 heat developed at a high temperature during the combustion is made 

 available for the work in hand. 



As it is now several years since your presidential chair has been 

 occupied by a professed physicist, it may naturally be expected that 

 I should attempt some record of recent progress in that branch of 

 science, if, indeed, such a term be applicable. For it is one of the 

 difficulties of the task that subjects as distinct as mechanics, electricity, 

 heat, optics, and acoustics, to say nothing of astronomy and meteor- 

 ology, are included under physics. Any one of these may well occupy 

 the life-long attention of a man of science, and to be thoroughly con- 

 versant with all of them is more than can be expected of any one 

 individual, and is probably incompatible with the devotion of much 



