316 Intelligence and Miscellaneous Articles, 



having a visible area — are those occupied by the planetary nebulae. 

 Of these, there is none which can be compared to Uranus in intrinsic 

 brightness, to say nothing of the moon. Supposing, then, our 

 system to be suddenly plunged into the bosom of one of these 

 nebulae, an increase of temperature would take place less than that 

 which would arise from superadding to our own that which the 

 surface of Uranus receives from the sun, or less than the 400th part 

 of that which we actually receive from it; and this supposes 

 Uranus to reflect all the light incident on it. 



" Leaving to others to judge, however, how far these arguments 

 are to be considered as militating against the view of climatological 

 changes in remote antiquity above alluded to, I may remark that it 

 is a matter of observed fact, that many stars have undergone in 

 past ages, within the records of astronomical history, very extensive 

 changes in apparent lustre, without a change of distance adequate 

 to producing such an effect. If our sun were ever intrinsically 

 much brighter than at present, the mean temperature of the surface 

 of our globe would, of course, be proportionally greater. I speak 

 now not of periodical, but of secular changes. But the argument 

 is complicated with the consideration of the possibly imperfect 

 transparency of the celestial spaces, and with the cause of that im- 

 perfect transparency, which may be due to material non-luminous 

 particles diffused irregularly in patches analogous to nebulae, but of 

 greater extent — to cosmical clouds, in short — of whose existence we 

 have, I think, some indication in the singular and apparently ca- 

 pricious phenomena of temporary stars, and perhaps in the recent 

 extraordinary sudden increase and hardly less sudden diminution of 

 ri Argus'* 



Elements of the comet visible at this period, computed by Dr. 

 Petersen, and received from Prof. Schumacher ; and parabolic ele- 

 ments of the same computed by Prof. Henderson, are given in the 

 Monthly Notice for January. 



XLV. Intelligence and Miscellaneous Articles. 



DETECTION OF IODATE OF POTASH IN IODIDE OF POTASSIUM. 

 BY MAURICE SCANLAN, ESQ. 



IT appears that hydriodic acid is sometimes exhibited as a thera- 

 peutic agent, and the method resorted to for its extemporane- 

 ous preparation is that recommended by Dr. Andrew Buchanan, 

 of Glasgow. It consists in mixing together, in proper proportion, 

 iodide of potassium and tartaric acid, both in solution. 



Now, the quantity of free iodine liberated from this salt, which 

 I have under examination, when treated with tartaric acid, in the 

 way just mentioned, has led some dispensing chemists to suppose 

 that it contains more iodine than other specimens of iodide of 

 potassium, which, when treated in a similar way, afford a solution 

 that is colourless, or, at most, of a very pale yellow colour ; and 

 hence, as I am informed, some actually look upon tartaric acid as a 



