isa-normaladvance-1909-00013

Description:	THE NORMAL ADVANCE13anvil to cool. Soon, a strange buzzing soundwas heard in that direction, which was tracedto the hot silver, quivering upon the anvil.A man named Schwartz observed this, but noexplanation was afforded at the time. Manyyears afterwards, Mr. Arthur Trevelyanchanced to be using a soldering iron, which helaid by accident against a piece of lead. Directly his attention was excited by a singularsound, which, after some searching, was foundto proceed from the soldering iron. Like thesilver of Schwartz, the iron was in a state ofvibration. Mr. Trevelyan made his discoverythe subject of much investigation and inventedthe Trevelyan Instrument or rocker as thevibrating mass is now called,- the movement ofwhich is produced by alternate* expansion andcontraction at different points of the metalupon which the instrument is laid. Here heatis converted directly into sound. Mr. Geo.Gore went a step further, and using the sameidea, made an interesting experiment. He tooka light metal ball and laid it upon two metalrails, lying horizontally parallel and so closeto each other as to support it. Beginning atone end of the rails, and heating them gradually toward the other, the ball was made toroll along by the wave of expansion, thus againobtaining locomotion from heat without employing steam.Lest we forget what we owe to this principle of expansion and contraction, it might bewell to speak of an instance that nature herselfperformed on a large scale. Geology tells usthat at one time our planet was in a state offusion—a molten mass that in cooling it contracted after a time a thin cooled crust wasformed the contracting center pulled awayfrom this, thus causing it to fold and wrinkle,forming ridges and folds, from which mountains, gorges, hills and valleys, and all the diverse features of the earth have been carved.But, suppose that the law of contraction bycooling had not been in force. Then the moltenmass had retained its size its surface had remained rigid instead of diversity and grandeur of scenery—instead of mountain and valley, hill and graceful slope, there had been onedreary monotonous, uninhabitable plain. Or,worse still, the water of the earth, (assumingthat there had been water), had not been gathered together in one place to let the dry landappear, but had spread its waste over theworld,—one vast boundless ocean. Then youand I, had we existence at all, had been fishesinhabiting a shoreless sea.Some practical uses that man has made ofthe law in consideration may be mentioned.Here belongs the metal thermometer in theshape of a bar, made of metals of differentco-efficients of expansion, and carrying a graduated arc to record the temperature. So alsodoes the Bologna glass phial in which the tension of its surface, due to unequal contraction,is so great, that a mere scratch will cause it tobe ground to powder or the Prince Rupertdrop, the breaking off the tail of which explodes it into dust. Wheelwrights use theprinciple of contraction in setting tires, andout-of-plumb Avails of brick and stone arebrought back into line by this all but irresist-able force.But Nature, with all her regularity andorder, is also rich in anomalies. From thestudy of a vast number of bodies, we should beled to conclude that heat always produces expansion in solids. But it is a fast rule, indeed,that has no exception. If a piece of commonvulcanized, India-rubber tubing be stretchedit produces heat instead of cold if allowed tocontract, it produces cold instead of heat. Heatapplied to India-rubber contracts it cold expands it. This is merely one of Natures littlesurprises.We have next to consider the expansion ofliquids. A common experiment is to heat aquantity of water in a Florence flask. Thelevel of the water falls at first on account ofthe more rapid expansion of the glass. Butafter a time it begins to rise and the expansioncontinues up to the boiling point. If for thewater, alcohol be substituted, it will show astill greater expansion. If liquid carbon diox-
Source:	http://indstate.contentdm.oclc.org/cdm/ref/collection/isuarchive/id/34043
Collection:	Indiana State University Archives

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