Prof. Draper's Description of the Tithonometer. 219 



When, on the sentient tube of the tithonometer,. the image of 

 a lamp formed by a convex lens is caused to fall, the liquid in- 

 stantly begins to move over the scale, and continues its motion 

 as long as the exposure is continued. It does not answer to ex- 

 pose the tube to the direct emanations of the lamp without first 

 absorbing the radiant heat, or the calorific effect will mask the 

 true result. By the interposition of a lens this heat is absorbed, 

 and the tithonic rays alone act. 



If a tithonometer is exposed to daylight coming through a 

 window, and the hand or a shade of any kind is passed in front 

 of it. its movement is in an instant arrested ; nor can the shade 

 be passed so rapidly that the instrument will fail to give the 

 proper indication. 



The experimenter may further assure himself of the extreme 

 sensitiveness of this mixture by placing the instrument before a 

 window, and endeavoring to remove and replace its screen so 

 quickly that it shall fail to give any indication ; he will find that 

 it cannot be done. 



Charge a Leyden phial, and place the tithonometer at a little 

 distance from it, keeping the eye steadily fixed on the scale ; 

 discharge the jar, and the rays from the spark will be seen to ex- 

 ert a very powerful effect, the movement taking place and ceas- 

 ing in an instant. 



This remarkable experiment not only serves to prove the sensi- 

 tiveness of the tithonometer, but also brings before us new views 

 of the powers of that extraordinary agent, electricity. That en- 

 ergetic chemical effects can thus be produced at a distance by an 

 electric spark in its momentary passage, effects which are of a 

 totally different kind from the common manifestations of electri- 

 city, is thus proved ; these phenomena being distinct from those 

 of induction or molecular movements taking place in the line of 

 discharge, they are of a radiant character, and due to the emission 

 of tithonicity ; and we are led at once to infer that the well known 

 changes brought about by passing an electric spark through gase- 

 ous mixtures, as when oxygen and hydrogen are combined into 

 water, or chlorine and hydrogen into muriatic acid, arise from a 

 very different cause than those condensations and percussions by 

 which they are often explained, a cause far more purely chemical 

 in its kind. If chlorine and hydrogen can be made to unite si- 

 lently by an electric spark passing outside the vessel which con- 



