TRANSACTIONS OF SECTION G. 725 



tions on the free movement of some, if not all, of the particles ; internal stresses are 

 developed which slowly assert themselves, and often cause unexpected failures. 

 In the manufacture of dies for coining purposes, of chilled rollers, of shot and 

 ehell hardened in an unequal manner, spontaneous fractures take place without any 

 apparent cause, and often after long delay, the reason being that the constrained 

 molecular motion of the inner particles gradually extends the motion of the outer 

 ones until a solution of continuity is caused. 



Similar stresses occur in such masses as crank shafts, screw shafts, gun hoops, 

 &c. The late General Kalakoutsky some seventeen years ago commenced a 

 systematic investigation into the internal stresses in the tubes and hoops of guns 

 and in armour-piercing shells. The method he pursued was to cut discs or rings 

 about half an inch thick off the hoops and shells, to divide the metal of each disc into 

 from four to six rings, to fix by means of silver plugs, on which very finely marked 

 cross-lines were drawn, from four to eight points on the surface of each ring, and then 

 to measure, with extreme exactness, the changes in diameter produced in every rino- 

 by the successive cutting out of the rings. Knowing by direct tests the mechanical 

 properties of his material, he was able, from the changes in the diameters, to calculate 

 what the tangential stresses in every part of each disc were, and to draw inferences 

 as to their fitness for the work they were intended to perform. The same method 

 of investigation has been pursued by Captain Noble of the Elswick Works, and 

 by Lieutenant Crozier of the United States artillery, with the practical result that 

 probably much more attention will be paid in future to the principles on which 

 the annealing and hardening of steel is carried on. A gun hoop or tube, to be in 

 the best condition to resist a bursting stress, should have its inner surface in a 

 state of compression, and its outer in a state of tension, and the hoops should be 

 •shrunk on to the tubes or on to each other with but very little pressure. General 

 Kalakoutsky proposed, in order to set up beneficial internal stresses, that tubes which 

 were being annealed should be cooled from the inside by a jet of steam, of air, of 

 "water, or of oil ; and he advocated the practice of testing the effects of each new 

 method of manufacture or of treatment by the careful measurements of slices of the 

 finished material instead of working at random, as is still very much the prac- 

 tice. It is evident, also, that a sample of steel cut out of a gun hoop or crank 

 shaft, and tested, can afford no indication of the available tenacity of the same 

 sample m situ. When released from the constraint of its surroundings, the par- 

 ticles must, of necessity, change their condition, for the disturbing forces have been 

 removed ; and the probability is that, if the steel be good, the test will prove satis- 

 factory, especially if some time be allowed to elapse between cutting out the 

 sample and testing it, and a false security will be engendered such as has often led 

 to disastrous results. 



The influence of time on steel seems to be well estabHshed ; the highest quali- 

 ties of tool steel are kept in stock for a considerable period ; and it seems certain 

 that bayonets, swords, and guns are liable to changes which may account for some 

 •of the unsatisfactory results which have manifested themselves at tests repeated 

 after a considerable interval of time. As all these things have been hardened and 

 tempered, there must necessarily have been considerable constraint put upon the 

 freedom of motion of the particles. This constraint has gradually been overcome, 

 but at the expense of the particular quality of the steel which it was originally 

 intended to secure. 



I have now laid before you the views respecting the constitution of matter 

 ■which I think are gaining ground, which explain many phenomena with which we 

 are familiar, and which will serve as guides in our treatment of metals, and espe- 

 cially of alloys ; but I must admit that the subject is still by no means clear, that 

 a great deal more definition is wanted, and that we ai-e stifl awaiting the advent 

 ■of the man who shall do for molecular physics what Newton did for astronomy in 

 explaining the structure of the universe. 



One of the most remarkable features of the last thirty years is the introduction 

 of petroleum, and the wonderful development to which the trade in it has 

 attained. 



Under the generic name of petroleum are embraced a vast variety of combi- 



