March 17, 1881J 



NA TURE 



465 



into a small bulb which is partly fiUed with glycerine, this 



mercuiy column. A wire fused into the main bulb of the 

 thermometer is connected with a binding-screw from 

 which a wire leads to one pole of a battery of two 

 Leclanch^ cells, the opposite pole of the battery being 

 placed permanently to eanh. 



If the free end of a wire, put to earth through a gal- 

 vanometer or bell, is brought successively in contact with 

 the binding-screws at the side of the thermometer, com- 

 mencing at the lowest, a signal will be given from each 

 wire in contact with the mercurial column, but not from 

 the wires above it. By carrying a conducting wire from 

 each of the binding-screws to a series of ordinary electrical 

 bell-pushes arranged on a key-board, the main bar of 

 which is put to earth through a signalling apparatus, it is 

 evidently possible to ascertain at any distance from the 

 thermometer the height of the mercury column, and 

 consequently the temperature, the mean error of observa- 

 tion depending upon the intervals between the wires 

 inserted in the bore of the thermometer. Such a form of 

 apparatus is however inconvenient, as it necessitates 

 carrying a large number of insulated wires to the observing 

 station. 



To avoid this difficulty I have devised the tninsmitting 

 portion of the instrument, an apparatus which, placed as 

 near as is convenient to the source of heat, is capable of 

 collecting the various signals from as many different 

 thermometers as may be desired, and of transmitdng all 

 these signals down a single wire to an observing station 

 at any required distance. This part of the apparatus, 

 sho\vn in Fig. 2, was constructed for me by Messrs. 

 Tasker and Sons of Sheffield. It consists essentially of 

 an ebonite ring, through the thickness of which are 

 inserted, at even distances, a series of small platinum 

 studs, terminating level with the surface of the ebonite 

 ring, and connected at the lower side with a series of 

 binding-screws arranged round the circumference of the 

 circular wooden frame enclosing the instrument. Within 

 iquid of course also fining the bore of the tube above the j the case of the instrument is an ordinary clockwork 



Thermometer 



^fiie Soi' Starting 



Line Itire for Siy\ 



'B atttru 



XESe/rth 



Earth 



"I^^'w 'I""'"" ^ ,.small metallic traverser, a( hich is I the hand of a watch. This traverser, furnished at its 

 v-apame of a somewhat rapid movement similar to that of | extremity with a small piece of platinum, is caused, by 



