Part 33 (1/2)

My contrivance consisted of an arrangement by means of which the metal bar or other solid substance, whose total expansion under a given nurees of heat had to be measured, was in a manner itself converted into a thermometer Absolutely equal bulks of each solid were placed inside a metal tube or vessel, and surrounded with an exact equal quantity of water at one and the sa a suitable length of thermometer tube attached to it, was then screwed down, and the water of the index tube was adjusted to the zero point of the scale attached to it, the whole being at say 50deg of heat, as the normal temperature in each case The apparatus was then heated up to say 200deg by immersion in water at that temperature The expansion of the enclosed bar of metal or other solid substance under experiment caused the water to rise above the zero, and it was accordingly so indicated on the scale attached to the cap tube In this e had a ther filled with the solid under investigation,--the water surrounding it i as the means by which the expansion of each solid under trial was rendered visible, and its a ascertained and recorded with the utmost exactness, as the expansion of the water was in every case the same, and also that of the instrument itself which was ”a constant quantity”

In this e obtained the correct relative amount of expansion in bulk of all the solid substances experimented upon That each bar of metal or other solid substance was of absolutely equal bulk, was readily ascertained by finding that each, eighed in water, lost the exact sae] James Nasmyth's Expansometer, 1826

My friend, Sir David Brewster, was soand description of it in the Edinburgh Philosophical Journal, of which he was then editor

1827 A Method of increasing the Effectiveness of Steae froine

One or the earliestwater, in a liquid for with the steaine

The first stea oil colours for ine to work for the first tiht jerks which now and then disturbed the otherwise sular action of the machine

After careful examination I found that these jerks were caused by the small quantities of water that were occasionally carried along with the current of the steam, and deposited in the cylinder, where it accumulated above and below the piston, and thus produced the jerks

In order to reularities, I placed a considerable portion of the length of the pipe which conveyed the steahly heated side flue of the boiler, so that any portion of water in the liquid forht, ere it reached the cylinder, traverse this highly-heated stea so, be converted into perfectly dry stea this siement into practice, I found the result to be in every way satisfactory The active little steaine thence-forward perforular manner

So far as I am aware, this early effort of mine at mechanical contrivance was the first introduction of what has since been termed ”super-heated stea iines

Without such ines, the latter are specially liable to ”break-downs,” resulting fro into the cylinders along with the stea” delicate Metal-work, in order that itportions of work in the turning-lathe, one of the most important points to attend to is, that while they are held with sufficient firmness in order to be turned to the required forht in any way distort the and ponderous objects this can be easily accoent work by the lathe on delicate and flexible objects that the ut, as they are easily strained out of shape by fastening them by screws and bolts, or suchlike ordinary means This is especially the case with disc-like objects As I had on several occasions to operate in the lathe with this class of work I contrived athe required turning process, which has in all cases proved most handy and satisfactory

Thisthree, or, if need be,them down on a tinned face-plate or chuck, which had been heated so as just to cause the solder to flow As soon as the solder is cooled and set, the chuck with its attached work may then be put in the lathe, and the work proceeded with until it is co upon it a piece of red-hot iron, the work, however delicate, can be simply lifted off, and will be found perfectly free from all distortion

I have been thethe use of three points of attachment to the chuck or face-plate, as that number is naturally free from any risk of distortion I have on so reat value of this si delicate work in the lathe, that I feel sure that any one able to appreciate its practical value will be highly pleased with the results of its employment

The sa delicate work in the planing-ht-iron or brass fixing-plate, to which the work in hand can be attached at a few suitable parts with soft solder, as in the case of the turning lathe above described

1828 A Method of casting Specula for Reflecting Telescopes, so as to ensure perfect Freeness fro the Brilliancy of the Alloy

My father possessed a very excellent achrolass was made by the celebrated Raaze at the h this instrueneral characteristic details of these grand objects, ave me a wonderful account of what he had seen of thetelescope of 12 inches diameter, made by Short-- that justly celebrated pioneer of telescopeIt had been erected in a teh These descriptions of ht of the glorious objects in the heavens through a lass, that I deterht in soly searched for the requisite practical instruction in the pages of the Encyclopedia Britannica, and in other books that professed to give the necessary technical information on the subject I found, however, that the inforiven in books--at least in the books to which I had access was re and unsatisfactory Nevertheless I set to ith all earnestness, and began by co a speculum of 8 inches diameter This alloy consisted of 32 parts of copper, 15 parts of grain tin, and 1 part of white arsenic

These ingredients, when ether, yielded a coree of brilliancy Having made a wooden pattern for my intended 8-inch diameter speculu telescope speculu to the best book instructions I allowedto cool in the mould in the slowest possible manner; for such is the excessive brittleness of this alloy (though cohest of e of te it, it is very apt to give way, and a fracture lass, brittle though it be, is strong in coh, as I have said, it yields thethe observance of all due care in respect of the annealing of the casting by slow cooling, and the utrinding the surface into the requisite curve and smoothness suitable to receive the final polish,-- I was on more than one occasion inexpressiblyup of my speculum Thus many hours of anxious care and labour proved of no avail I had to begin again and proceed da capo I observed, however, that the surplus alloy that was left in the crucible, after I had cast ot ht be, was yet strong in comparison with that of the speculu froher degree of brilliancy

The happy thought occurred toan open metal mould for the closed sand one I soon had the

It consisted of a base plate of cast iron, on the surface of which I placed a ring or hoop of iron turned to fully the diameter of the intended speculum, so as to anticipate the contraction of the alloy

The result of the very first trial of this simple metal mould was : and it passed successively through the ordeal of the first rough grinding, and eventually through the processes of polishi+ng, until in the end it exhibited a brilliancy that far exceeded that of the sanddifficulty that I had to surmount was the risk of defects in the surface of the speculum These sometimes result from the first splash of the lobules soot oxidised before they beca y spots in the otherwise brilliant alloy were thus produced I soonsource of defect, by a very si thepocket;”

which co, and by a self-acting arrangehtly tilted up, the influx of the molten alloy advanced in one unbroken tide As soon as the entire surface of the ht overca counterpoise, and allowed the entire apparatus to resu speculuements, absolutely perfect in soundness It was a perfect casting, in all respects worthy of the care and labour which I invested in its future grinding and polishi+ng, and enabled it to perforrand essential part of a noble reflecting telescope!

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