THE POPULAR SCIENCE MONTHLY. 



again in his own inventions, which were 

 in turn to give a further impulse to sci- 

 entific work. A very large proportion 

 of the engineer's success was due to his 

 regarding infinitesimals ; and in respect 

 to this point it was appropriate for the 

 speaker to show how greatly infinitesi- 

 mals or " next-to-nothings " determine 

 the strength, the fitness, and the dura- 

 bility of works and materials. Take 

 the case of steel, which in times that are 

 not very old was dealt with and tested 

 in a " rule-of-thumb " fashion. It was 

 known to be a compound of iron and 

 carbon — 



'•but the importance of exactness in the per- 

 centage was but little understood, nor was it 

 at all understood how the presence of com- 

 paratively small quantities of foreign matter 

 might necessitate the variation of the propor- 

 tions of carbon. The consequence was, that 

 anomalous results every now and then arose 

 to confound the person who had used the 

 steel, and, falsifying the proverb 'true as 

 steel,' steel became an object of distrust. Is 

 it too much to say that Bessemer's great in- 

 vention of steel made by the ' converter,' and 

 that Siemens' s invention of the open-hearth 

 process, reacted on pure science, and set sci- 

 entific men to investigate the laws which regu- 

 late the union of metals and of metalloids, and 

 that the labors of these scientific men have 

 improved the manufacture, so that steel is 

 now thoroughly and entirely trusted ? By 

 its aid engineering works are accomplished 

 which, without that aid, would have been 

 simply impossible. The Forth Bridge, the 

 big gun, the compound armor of the ironclad 

 with its steel face— all equally depend upon 

 the ' truth ' of steel as much as does the barely 

 visible hair-spring of the chronometer, which 

 enables the longitude of the ship in which 

 it is carried to be ascertained. Now, what 

 makes the difierence between trustworthy and 

 untrustworthy steel for each particular pur- 

 pose? Something which, until our better 

 sense comes to our aid, we are inclined to look 

 upon as ridiculously insignificant — a ' next-to- 

 nothing.' Setting extraneous ingredients 

 aside, and considering only the union of iron 

 and carbon, the question whether there shall 

 be added or deducted one tenth of one per 

 cent of carbon is a matter of great importance 

 in the resulting quality of the steel. This is 

 a striking practical instance of how apparent- 

 ly insignificant things may be of the highest 

 importance. The variation of this fraction of 



a percentage may render your boiler-steel un- 

 trustworthy, may make the difference between 

 safety in a gun and danger in a gun, and may 

 render your armor-piercing projectile unable 

 to pierce even the thinnest wrought-iron 

 armor." 



So the effects upon steel of adding man- 

 ganese — whether it shall improve or de- 

 teriorate the metal — are matters of rath- 

 er delicate calculation — 



"and the effects of the addition of even the 

 very smallest percentages of aluminum upon 

 the steel with which it may be alloyed are 

 very striking and very peculiar, giving to the 

 steel alloy thus produced a very much greater 

 hardness, and enabling it to take a much 

 brighter and more silver-like polish. Fur- 

 ther, the one twentieth part of one per cent of 

 aluminum, when added to molten wrought- 

 iron, will reduce the fusing-point of the whole 

 mass some five hundred degrees, and will 

 render it extremely fluid." 



The engineer engaged in electrical 

 matters is also often compelled to real- 

 ize the importance of the " next-to-noth- 

 ing," as in the case of the influence 

 which an extremely minute percentage 

 of impurity has on the electrical con- 

 ductivity of copper wire. This con- 

 ductivity is, in some cases, reduced as 

 much as fifty per cent, in consequence 

 of the admixture of that which, under 

 other circumstances, would be looked 

 upon as insignificant. 



The internal strain which a great 

 gun may suffer in the process of oil- 

 hardening, by the operation of which it 

 may be self- ruptured months afterward, 

 is gauged in the most minute fractions 

 of an inch. The various degrees to 

 which a tool is tempered according to 

 the uses to which it is to be adapted, 

 all depend upon the "next-to-nothing" 

 differences in the temperature to which 

 the metal is heated. Then — 



"consider the bicycles and tricycles of the 

 present day — machines which alford the 

 means of healthful exercise to thousands, and 

 which will probably, in a very short time, 

 prove of the very greatest possible use for. 

 military purposes. The perfection to which 

 these machines have been brought is almost 

 entirely due to strict attention to detail ; in 



