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 way we had a thermometer whose bulb was for the time being filled with the solid under investigation, -- the water surrounding it imply acting as the means by which the expansion of each solid under trial was rendered visible, and its amount capable of being 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 way we 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, when weighed in water, lost the exact same weight.

James Nasmyth's Expansometer, 1826.

My friend, Sir David Brewster, was so much pleased with the instrument that he published a drawing and description of it in the Edinburgh Philosophical Journal, of which he was then editor.

A Method of increasing the Effectiveness of Steam by super-heating it on its Passage from the Boiler to the Engine.

One or the earliest mechanical contrivances which I made was for preventing water, in a liquid form, from passing along with the steam from the boiler to the cylinder of the steam-engine. The first steam- engine I made was employed in grinding oil colours for my father's use in his paintings. When I set this engine to work for the first time I was annoyed by slight jerks which now and then disturbed the otherwise smooth and regular 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 remove the cause of these irregularities, I placed a considerable portion of the length of the pipe which conveyed the steam from the boiler to the engine within the highly heated side flue of the boiler, so that any portion of water in the liquid form which might chance to pass along with the steam, might, ere it reached the cylinder, traverse this highly-heated steam pipe, and, in doing so, be converted into perfectly dry steam, and in that condition enter the cylinder. On carrying this simple arrangement into practice, I found the result to be in every way satisfactory. The active little steam-engine thence- forward performed its work in the most smooth and regular 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 steam" -- a system now extensively employed, and yielding important results, especially in the case of marine steam-engines. Without such means of supplying dry steam to the engines, the latter are specially liable to "break-downs," resulting from water, in the liquid form, passing into the cylinders along with the steam.

A Method of "chucking" delicate Metal-work, in order that it may be turned with perfect truth

In fixing portions 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 form, they should be free from any strain which might in any way distort them. In strong and ponderous objects this can be easily accomplished by due care on the part of an intelligent workman. It is in operating by the lathe on delicate and flexible objects that the utmost care is requisite in the process of chucking, 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 a method of chucking or holding them firm while receiving the required turning process, which has in all cases proved most handy and satisfactory.