292 Prof. Doebereiner un his u-cit.^ Experiments. 



several preparations of platinum. That the continuation of 

 the experiments on this interesting subject would lead to new 

 discoveries, was to be expected. I merely mention to-day, 

 that I have succeeded in making the observed dynamic rela- 

 tion of the platinum powder to the hydrogen gas, appear in 

 a very splendid manner by experiment. If hydrogen gas be 

 suffered to issue from a gasometer through a capillary tube 

 bent downAvai'ds, upon the platinum contained in a small 

 glass funnel sealed at the bottom, so that the stream may mix 

 with the atmospheric air before it comes in contact with the 

 platinum, which is effected when the tube is from 1 to 1^ 

 or 2 inches distant from the platinum, the latter almost in- 

 stantly becomes red- and white-hot, and remains so, as long 

 as the hydrogen continues to flow upon it. If the stream of 

 gas be strong, it becomes inflamed, particularly if it has al- 

 ready been mixed in the reservoir with some atmospheric air. 

 This experiment is very surprising, and astonishes every be- 

 holder, when he is informed, that it is the result of the dy- 

 namic reaction of two species of matter, one of which is the 

 lightest and the other the most ponderous of all known bo- 

 dies. That I have already applied this new discovery to the 

 formation of a new apparatus for procuring fire, and of a new 

 lamp ; and that I shall avail myself of it for much more im- 

 portant purposes, you may well suppose beforehand: — more 

 of it in my next. Dcebereineii. 



LXI. On the Parallax of « Lyra;. By John Pond, JLsq. 



Astronomer Royal, F.R.S. * 

 IV/TY former experiments with a fixed telescope upon a 

 Cygni have always appeared to me so decisive, as to ren- 

 der hopeless any further attempt to discover its parallax ; but 

 respecting that of « Lyrse, my observations with the mural 

 circle were not equally satisfactory ; for among the observa- 

 tions of this star we may find occasional discordances that 

 admit of being interpreted in favour of parallax. And although 

 I have been inclined myself to attribute these irregularities to 

 other causes, yet their existence made it desirable to institute 

 new experiments. The method with a fixed telescope, which 

 I had contrived for « Cygni, could not here, I found, be ap- 

 plied successfully ; there being no star of nearly the same al- 

 titude but opposite in right ascension sufiiciently bright to be 

 observed throughout the year, a circumstance quite essential 

 to that mode of observation. I have employed therefore the 

 mural circle to investigate, 1st, the difference of parallax be- 



* From the Philosophical Transactions for 1823, Part I. 



tvveen 



