NATURAL PHILOSOPHY. 165 



The part of the instrument forming the thermometer proper consists of a 

 cylindrical bundle of iron and brass wires (No. 13), about fifteen inches in 

 length, so arranged as to be equivalent to about forty-five inches of iron wire 

 antagonized by about an equal length of brass wire. The bundle is composed 

 of five pairs, two of brass and three of iron, arranged alternately around 

 the centre, and a single wire of brass, equivalent in action to a third pair of 

 that metal, placed in the axis of the cylinder. The upper end of the central 

 wire, moved by the difference of expansion of the two metals, operates upon 

 the short arm of the first of a train of two levers, and through them upon 

 the axle of a pulley. To the grooved circumference of the larger wheel of 

 tin's pulley is attached a slender silk cord, carrying the registering point 

 designed to mark the temperature, and which, by the multiplying effect of the 

 mechanism, is moved over a space three hundred and twenty times as great 

 as the differential expansion or contraction of the wires. The registering 

 point, properly balanced by an attached weight, and guided in its vertical 

 movements by two slender parallel rods, is made to record the temperature 

 on a fillet of paper moved by a train of cylinders whose axes are parallel to 

 the guide-wires. The record is impressed by the impulse of a hammer strik- 

 ing upon the back of the registering point at regulated intervals, and thus 

 producing a series of small perforations in the paper, the hammer and the 

 fillet of paper both receiving their motion from a train of clock-work, of 

 peculiar construction, connected with the apparatus. 



The projecting shaft of the pulley carries an index, which, revolving in 

 front of a dial-plate placed over the pulley, enables the observer to note the 

 temperature as compared with the ordinary thermometer, and to adjust the 

 rod-thermometer to the standard whenever necessary. The adjustment is 

 made by turning a screw connected with the lower end of the central brass 

 wire of the thermometer. The latter instrument is on the outside of the case 

 which incloses the dial, registering apparatus, and clock. By a peculiar 

 arrangement of the clock-work, the hammer movements, and therefore the 

 times of registration,, may be adjusted to quarter-hour, half-hour, or hour 

 intervals, and may be changed from one to the other at the will of the 

 observer. 



The above description is derived from a report made to the Boston Society 

 of Natural History, by Professor W. B. Rogers, who also takes occasion to 

 recommend the instrument as worthy the critical examination of men of 

 science, and one which, from its great sensitiveness and accuracy, promised 

 to become a valuable help in meteorological observations. 



Beaumont's new Metallic Thermometer. The principle of a new thermom- 

 eter recently invented by Victor Beaumont, of New York, is the dilatation of 

 different metals. A straight strip of brass and a similar strip of steel are 

 soldered together; when heated, the compound strip expands more on the 

 brass side than on the other, hence bends in a curve. One end of the strip 

 is made fast to the case; the other end is connected, by means of a link and 

 a crank, to the spindle which carries the hand. The crank is provided with 

 a regulating screw, by means of which the range of motion is made to cor- 

 respond with the graduation on the dial; and the whole machinery of the 

 spindle is carried on a stand, which is moved by another screw, to set the 

 instrument after a standard. This setting screw is reached from the outside, 

 and if the thermometer gets out of order it may easily be set to work cor- 

 rectly by means of a screw-driver. The external appearance of the instru- 

 ment is that of a watch, four inches diameter, with a Fahrenheit and a ceuti- 



