Tll.VNSACTIOXS OF THE SECTION'S. 20o 



and relative .strengtli of the new material as compared witli irou, sucli a girder 

 would assm'edly collapse when the test-weight was applied, for the simple reason 

 that the reduced sectional area of each part, in proportion to its length, would be 

 insufficient to give stilihess. You might as well almost take a design for a wooden 

 structure and carry it out in iron by simply reducing the section of each part. The 

 advantages of using the stronger material become most apparent if applied, for in- 

 stance, to large bridges, where the principal strain upon each part is produced by 

 the weight of the structure itself; for, supposing that the new material can be 

 safely weighted to double the bearing strain of iron, and that the weight of the 

 structure were reduced to one-half accordingly, there would still remain a largo 

 excess of available strength, in consequence of the reduced total weight, and this 

 would justify a further reduction of the amount of the material employed. In con- 

 structing works in foreign parts, the reduced cost of carriage furnishes also a pow- 

 erful argument in fa\our of the stronger material, although its first cost per ton 

 might largely exceed that of iron. 



The inquiries of the Koyal Coal Commission into the extent and management 

 of our coal-fields appear to be reassuring as regards the danger of their becoming 

 soon exhausted ; nevertheless, the importance of economising these precious de- 

 posits in the production of steam-power in metallurgical operations and in domes- 

 tic use can hardly be over-estimated. The calorific power residing in a pound of 

 coal of a given analysis can now be accurately expressed in units of heat, which 

 again are represented by equivalent units of force or of chemical action ; therefore, 

 if we ascertain the consumption of coal of a steam-engine or of a furnace employed 

 in metallurgical operations, we are able to tell, by the light of physical science, 

 what proportion of the heat of combustion is utilized and what pi'oportion is lost. 

 Having arrived at this point we can also trace the channels through which loss 

 takes place, and in diminishing these, by judicious improvement, we shall more 

 and more approach those standards of ultimate perfection which we can never 

 reach, but which we should nevertheless keep stedfastly before our eyes. Thus 

 a pound of ordinary coal is capable of producing 12,000 (Fahrenheit) units of heat, 

 which equal 9,240,000 foot-lbs. or imits of force, whereas the ^-ery best perform- 

 ances of our pumping engines do not exceed the limit of 1,000,000 foot-lbs. of 

 force per pound of coal consumed. In like manner 1 lb. of coal should be capable 

 of heating -33 lbs. of iron to the welding-point (of, say, o000° Fahrenheit), whereas, 

 in an ordinary furnace, not 2 lbs. of iron are so heated with 1 lb. of coal. These 

 figures serve to show the great field for further improvement that lies yet before us. 



Although heat may be said to be the moving principle by which all things in 

 nature are accomplished, an excess of it is not only hurtful to some of our processes, 

 such as brewing, and destnictive to our nutriments, but to those living in hot 

 climates, or sitting in crowded rooms, an excess of temperature is fully as great a 

 source of discomfort as excessive cold can be. Why then, may I ask, should we not 

 resoii; largely to refrigeration in summer as well as to calorihcation in winter, if it 

 can be shown that the one can be done at nearly the same cost as the other ? So long 

 as we rely for refrigeration upon our ice-cellars, or upon importation of ice from 

 distant parts, we shall have to look upon it as a costly luxury only; but by the 

 use of properlv constructed machines, it will be possible, I believe, to produce re- 

 frigeration at an extremely moderate expenditure of fuel and labour. A machine 

 has already been constructed capable of producing 9 lbs. of ice (or its equivalent) 

 for 1 lb. of coal, whereas the equivalent values of positive heat developed in the 

 combustion of 1 lb. of coal and of negative heat residing in 1 lb. of ice is about as 

 12,000 to 170, or as 1 to 70. This result already justifies the employment of refri- 

 gerating machines upon a large scale ; but it is hard to say what practical results 

 may yet be reached with an improved machine on strictly dynamical principles, 

 because such a machine seems not to he tied in its results to any definite theoretical 

 limits. In changing, for example, a pound of water from liquid into the gaseous 

 state, a given number of units of heat are required, that may be produced by the 

 combustion of coal or by the expenditure of force ; but in changing the same 

 pound of water into ice, heat is not lost but gained in the operation, which heat 

 must be traceable to another part of the machine, either as sensible heat or as 

 developed force, It would lead me too far to enter here into particulars on this 



