TRANSACTIONS OF THE SECTIONS. 59 



musical sounds : and it is shown that for a given value of k there are three different 

 velocities of wave transmission, viz. one corresponding to the upper sign, and two to 

 the lower sign. This is what the author means by the triplicity of sound. The 

 papers on this subject will be found printed at length in the ' Philosophical Maga- 

 zine ' for June, July, and September. 



Instruments. 



Description of an Instrument for Measuring Actual Distances. 

 By Patrick Adie. 

 The telemeter consists of two telescopes so arranged in two concentric tubes, that 

 the rays formed by two object-glasses, at or near the extremities of the tubes, are by 

 means of reflectors brought together into one eyepiece in the middle of the tubes ; 

 thus both telescopes are simultaneously pointed at the same object, one being move- 

 able, and their relative angle taken from a scale and vernier, and this by reference 

 to a table on the instrument gives the distance of the object looked at. The author 

 has obtained measures to 5 yards in 500, and 20 in 1000 with a base of only 18 inches. 

 The length of the arm and power of the telescopes being equal to such minute accu- 

 racy, this promises to supply the link wanting to make the long range in gunnery use- 

 ful. Its power is such, that with the 18-inch base, the one described, we can read to 

 5 yards in 500, or 20 in 1000, and it may be used up to 4 or 5 miles with effect. 



Description of a New Reflecting Instrument for Angular Measurement. 



By Patrick Adie. 

 The instrument is a sextant or circle which the author proposed to name the bino- 

 cular reflector. It consists of two telescopes, also so arranged as to work with one 

 eyepiece, one telescope being directed to each of the objects whose angular distance 

 is sought; one of these is fixed below the limb, the other above it; and the rays are 

 passed from the lower into the upper, by means of a reflector sending them at right 

 angles through the centre of the instrument, which is hollow ; these rays entering 

 the upper telescope, are by means of a second reflector passed along with those of 

 the other half which is open into the eyepiece. The point of this instrument is, that 

 it gives the whole instead of half degrees as in Hadley's principle, thus reducing the 

 size of the instrument one-half, and the cost nearly in like degree; it will also be 

 much less subject to disarrangement, and can measure any angle up to 180°. 



On a Pile with Sulphate of Lead. By M. E. Becquerel. 

 The pile of M. Edmond Becquerel is composed of an exterior receiver of zinc of 

 an annular shape, and of a cylinder composed as follows. A cylinder of lead of 29 

 centimetres (finches) long and about half a centimetre ( T %thsof an inch) diameter, 

 is placed in the inside of a mould 13 centimetres (4-6 inches) in height, and 9 centi- 

 metres is filled (21 inches) in diameter, with a paste of sulphate of lead pulverized, 

 and 400 grammes water saturated with marine salt at 25° of the areometer, [being 

 129 to 139 cubic centimetres. The mixture of these should be made very quickly. 

 After the sulphate of lead has acquired a sufficient consistence, we remove it from the 

 mould, and we cover it round with a bed of plaster of half a centimetre in thick- 

 ness. This pile is charged with water rendered saline with common (sea) salt about 

 Jth saturated. Its electromotive force is equal to the half of that of sulphate of 

 copper, and its resistance to conduction is equivalent to 100 metres of red copper 

 wire of a millimetre diameter. It has the advantage of being very simple, and of 

 not requiring anything to keep it in action ; it is put into action by a single liquid, 

 and does not need a porous vessel. It possesses much constancy, and does not cease 

 to act until the sulphate of lead is entirely reduced to the metallic state. M. Bec- 

 querel had one in action composed often pairs, of which the circuit remained com- 

 pletely closed for three months. 



