Recent Advances in Mechanical Science. 153 



many phases. We had hoped at one time that a great future 

 was before a tubulous system of boiler, patented by the late Mr. 

 Perkins, where pressures up to 500 lbs. on the square inch were 

 carried, but before advising our friends to adopt this type we 

 fitted a complete engine and boiler indicating over 200 horse- 

 power in an old steamer, which worked fairly well for some 

 years, but eventually the whole plant had to be condemned for 

 a variety of reasons which at the present time I cannot detail. 

 Probably no boiler of this type is more satisfactory than the 

 design carried out by Messrs. Thorny croft for their torpedo 

 boats, but I have my doubts whether this style of boiler will 

 come into use for mercantile marine work. 



Great misapprehensions exist in the minds of many people 

 regarding the danger of working at high pressures, but their 

 fears are entirely unfounded. No structure, so far as the strain 

 brought to bear upon it is concerned, is better treated than a 

 boiler. Steam is got up very gradually, is kept up steadily, and 

 is again lowered very slowly. The only evils that are trouble- 

 some to deal with arise from expansion and contraction due to 

 differences of temperature in various parts of the boiler, and, 

 in former times especially, pitting of the internal surface of 

 the boilers. This has been discovered to originate from air in 

 the water, and has latterly been practically got rid of. 



But it is time for me to go to another branch of the subject. 

 I have mentioned electrical results. In a way, these dwarf all I 

 have outlined in the purely mechanical line. It is when the 

 two branches — electrical and mechanical — come together that 

 the feature of the coming age is made manifest. We are only 

 on the verge of what is before us from the result of the union 

 of these two sciences, especially when they are associated with 

 chemistry. Much has already been done by such men as 

 Siemens, Sir Wm. Thomson, and a hundred more clever 

 scientists in our own country to bring electricity to the front, 

 but all these discoveries and results obtained, however valuable, 

 are put in the shade by the wizard of Menlo Park — Edison. 

 He is by far the most prolific inventor of the age in that line. 



