1893.] Scientific tntelUgence. 467 



Herapath, in England: but these philosophers do not mention that 

 any other than substances actually in the metallic state are capable 

 of exhibiting a similar appearance. 



After repeating several of the experiments already published, I was 

 induced to submit a number of other bodies to the action of the 

 hydrogen jet. Some I found to have their temperature slightly in- 

 creased, and the greater number not at all : but the most remarkable 

 increase which I have observed lias been with the ore of iridium ; * 

 this substance, when previously heafed to redness and suffered to cool, 

 becomes red-hot by a stream of cold hydrogen, in the manner of 

 spongy platina, and appears to retain the property of so doing equally 

 well. 



The circumstance of these bodies becoming heated to incandescence 

 in our atmosphere of medium temperature, naturally suggests the idea 

 of employing them for the instantaneous production of fire and light ;f 

 but, in order that this may be done with tolerable certainty, so as to 

 be really useful, it becomes necessary that the effect shall take place 

 at pretty low temperatures. To ascertain this point 1 made the fol- 

 lowing experiments:— 



A quart bottle filled with hydrogen gas was placed in an earthen- 

 ware wine-cooler, and the space between the sides of the bottle and 

 of the cooler was filled up with ice, broken into small fragments, a 

 small piece of spongy platina was exposed upon a slip of foil of the 

 same metal, and laid upon the surface of the ice ; in this state the 

 whole was left in an apartment (at 52°) for about three quarters of the 

 hour ; at the end of this time the temperature of the platina foil was 

 found to be 35°, which, with the spongy metal, was covered with a 

 considerable film of moisture. 



A jet of gas was now made to pass from the bottle through a capil- 

 lary tube upon the spongy platina, the moisture immediately began 

 to evaporate, and the metal quickly became heated to whiteness, 

 kindling the hydrogen as it issued from the orifice of the tube. 



From the result of this experiment (which was made, not so much 

 with a view to determine the minimum temperature at which the effect 

 could be produced, as to see whether it would take place at the usual 

 degrees of atmospheric temperature in this climate,) it has appeared 

 that a very ready and elegant mode of obtaining light may be ob- 

 tained. 



I have constructed several lamps for the purpose upon a very 

 simple principle, and from the certainty which 1 have hitherto ob- 

 served, I have reason to believe that they will answer most completely. 

 When I have satisfied myself as to the most convenient form^ I shall 

 probably trouble you with a sketch of it, and also with the results of 

 a few more experiments upon the subject. 



I remain, dear Sir, your's truly, 



A. Garden. 



• I mean the black powder which remains after the action of nitro-muriatic acid 

 upon crude platinum, and which also contains osmium, 

 •j- Dicbereiner says, that he has already applied his discovery to this purpose. - 



2h2 



