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XXXIX, On the occurrence of Wulfenite in Kirkcudbrightshire, 

 By Dr. Heddle*. 



GREG and Lettsom doubt whether or not Wulfenite may- 

 rank as a British species. In Thomson's ' Mineralogy/ 

 vol. i. p. 565, we find the following remarks on a specimen (a 

 single specimen) in the possession of the Stockholm Academy : — 

 " It was ticketed lead-spar, from Mendip, near Churchhill in 

 Somersetshire ; it was chiefly carbonate of lead, but it contained 

 two portions of a yellower colour than the rest, which attracted 

 the particular attention of Berzeliusf. One of these being exa- 

 mined by the blowpipe, proved to be molybdate of lead. The 

 other portion was an oxido-chloride of lead." 



This, so far as I know, is the only published record of the 

 occurrence of this substance in Britain. Lately a new pit was 

 sunk for some 30 fathoms at the " South of Scotland Mines " at 

 Lackentyre, near Gateshead in Kirkcudbrightshire ; and among 

 several interesting minerals brought me thence by Mr. James 

 Russel of Airdrie, there was a single specimen of the molybdate. 

 The associated minerals are galena, carbonate and phosphate of 

 lead, and cupreous calamine ; the molybdate occurs in well-pro- 

 nounced and unusually brilliantly polished crystals of about one- 

 eighth of an inch in size; 

 the forms are csn and 

 csnm; the faces n and 

 m are very narrow : the * 

 crystals are thin, transpa- 

 rent, and bright yellow. 



The pit in which this 

 specimen was found proved Lackentyre. 



unproductive, and has been abandoned ; there is thus little hope 

 of others being obtained. 



XL. On the Heat disengaged by Induction-currents, and on the 

 relation between this disengagement of Heat and the mechanical 

 force employed to produce it. By M. E. EdlundJ. 



WHEN a closed conducting wire is brought near a galvanic 

 current, an induced current is produced in the former, 

 the direction of which is such that it would give rise to a repul- 



* Communicated by the Author. 



t Kong. Vet. Acad. Handl. 1823, p. 184. 



X The original memoir was published in the Comptes Rendus de I'Aca- 

 demie des Sciences de Stockholm, 1864, p. 79. The above article is the 

 translation of an abstract contained in the Bibliotheque Universelle, Decem- 

 ber 20, 1865. 



