Mr Nasmyth's Description of an Instrument, $c. 225 



ncous course, till they issue from the mountain into some lower 

 open hollow, as in the valley of Planina, or here in the lake of 

 Zirknitz. The quantity and size of the fish, which retire with 

 the lake into the caverns beneath, and return with the return- 

 ing stream, prove that there must be capacious reservoirs with- 

 in the bosom of the mountain, in which they can exist and pros- 

 per. 



Where the outlets of the lake finally discharge their waters 

 cannot, of course, be easily traced, because their subterrane- 

 ous channels cannot be followed ; but the whole country, from 

 the northern limits of Carniola to the shores of the Adriatic, 

 from the caverns of Planina to the sources of the Timavus, is 

 so full of streams, whose first appearance above ground implies 

 a previous subterranean course, that there is no difficulty in 

 accounting for the disappearance of the lake. The Jersero is- 

 suing from the cave of St Cantian, the Idria bursting from the 

 mountains not far from the mines, the Wippach rising in the 

 same manner farther to the westward, are, in all likelihood, 

 outlets of the Zirknitz. And what is there improbable in the 

 supposition, that even the Timavus itself draws part of its 

 stores from this alternating reservoir ? — RusseVs Tour in Ger- 

 many. 



Art. VII. — Description of an Instrument for Measuring the 

 Comparative Expansibility of Metals and other Solid Bo- 

 dies. By Mr James Nasmyth. Communicated by the 

 Author. 



This instrument consists of a glass tube, about one inch in 

 diameter, and about four inches long, sealed at one end. To 

 this tube is cemented a brass cap, the top of which is made to 

 screw off. To this top or cover is cemented a glass tube, about 

 three feet long, (such as that used for thermometers,) open at 

 each end. A scale of inches and tenths is attached to this tube. 

 In order to operate with this instrument, equal bulks of each 

 of the metals to be operated upon is to be procured, of such 

 dimensions as just to fill the glass tube A, Plate IV. Fig. 3, 

 but not tightly. The tube A is then to be filled with water at 



VOL. VI. NO. II. APRIL 1827- P 



