1814.] Scientific InteUigence, 75 



IV, On ike Method of drawing fine Platinum IVire. 



I have received the following letter on this subject, dated Edin- 

 burgh, Dec. 9, 1813 :— 



(To Dr. Thomson.) 

 SIR, 



In trying Dr. Wollaston's method of drawing fine platinum wire, 

 1 had considerable difficulty in casting the silver about the wire. 

 The following mtiliod is much easier than either boring the silver, 

 or casting it round the wire : — Bind the silver into a tube, and 

 draw it through a plate, as is done in making small hinges. A 

 piece of platinum wire pushed into this kind of tube may be drawa 

 to any degree of fineness. 



In one instance it was drawn so fine that when put into the 

 nitric acid, and the silver dissolved, the platinum remained in the 

 form of black floculi in the liquid. 



In attempting to hammer platinum in the gold-beaters' case, it 

 was soon broken to pieces. It may be made as thin as gold leaf, by 

 rolling it between a folded piece of sheet copper. When a number 

 of platinum leaves are rolled at once, leaves of copper should be 

 put between them, to prevent their adhering.* S. 



V. Astronomical Observations at Oxford. 

 In consequence of the notice on the wrapper of the last Number 

 of the Annals of Philosophy, respecting astronomical observations 

 at Oxford, I have received two communications on the subject, 

 equally remarkable for the difference of the information and of the 

 style. One Gentleman informs me that tlie Observatory at Oxford 

 is under the care of the Savilian Professor, that regular observations 

 are made, and that they have it in contemplation to publish them, 

 like those at Greenwich. The other Gentleman says, that my note 

 respecting this subject would not have been written if I had had 

 any value for my character; that if I had asked for information on 

 the subject, I might have had some details that would not have 



thai ligtit is polarized by refraction, as well as reflcclicdi. As Malus's paper on 

 this suhjcct ii aliort, and beems to be unknown in this country, 1 shall insert a. 

 translation of it in the next Number of the Annals of PlUlnsophy. It will 

 enable Dr. lircwsttT to judge how far he has been anticipated by the French phi- 

 luiopher. — T. 



• 1 have reason to bi-licve that my CorreispondeBt's method is not so good as Dr, 

 Wollaston's. Dr. Wollaston, I know, trird it without finding it to answer. The 

 black flocks which appe-ired when tiie silver was dissolved in nitric acid were 

 probably not owing to the finenc&s of the wire, but to llie badness of the mode of 

 drawing it. I think also there is strong reason to doubt the possibility of rollinir 

 out platinum to the lliinneiis of gold leaf. All Dr. Wollaslnn's friends must have 

 ofien seen the line platinum leaves which he formed some years ago by the same 

 prore>» as tli:it of my Corrcipondent. The plaiinnm is obviously as thin as it will 

 go, yet iheie u a prodigious dilTercnce between the thickness of these leaves and 

 coinmun gold leaf. N'lr med we be surjiiised at this, for gold itself could not be 

 rolled nut neatly «o thin av gidd leaf. The method of making gold leaf is quite 

 dillcieni.— T. 



