10 Spontaneous Fracture of Cast Iron. 



of lines, either of equal elevation (commonly called contour lines), or of 

 greatest and least declivity (or ridge and valley lines), according as may 

 be consonant to the practice adopted for other districts." 



" To the Clerk to the Commissioners of Supply of the County of- 



" SiE, — I am directed by the Council of the Philosophical Society of 

 Glasgow, to transmit to you the enclosed copy of a Memorial which 

 has been presented to the Lords of Her Majesty's Treasury by that 

 Society. 



" The Council of the Philosophical Society consider that the subject of 

 the Memorial is one well worthy of the attention of the Commissioners, 

 and that, should the Commissioners see fit to make a similar represen- 

 tation to the Lords of Her Majesty's Treasury, an important benefit 

 to the County may be secured. — I have, &c., 



" Secretary of the Philosophical Society of Glasgow." 



Lanark, Eenfrew, Dumbarton. 



Copy to the Town Clerks of Grlasgow, substituting " Town Council" 

 for " Commissioners of Supply," and " District surrounding Glasgow" 

 for " County." 



The President exhibited specimens of Cho Borealis, and several other 

 recent Pteropods, along with a specimen of Conularia quadrisulcata, 

 the only fossil species of Pteropod found in the coal formation. 



Mr. W, J. Macquorn Rankine brought under the notice of the 

 Society an instance communicated to him by Mr. William Smith 

 Dixon, of the spontaneous fracture of a mass of cast iron during a 

 sudden reduction of temperature. The block, which was cast at the 

 Govan ironworks, consisted of nine tons of metal, and split right down 

 the centre durmg a late hail-storm, when the temperature of the atmo- 

 sphere fell eight degrees in the course of five minutes, 



Mr. Condie mentioned that the block, which was a fine specimen of 

 iron, had been cooled by exposure to tlie open air for two or three days, 

 and the surface became wet with sleet during the hail-shower. He 

 remembered that some years ago, a mass of iron, thirty tons in weight, 

 after being finished, was laid on a waggon at Greenock, where it broke 

 to pieces from the efi'ect of a sudden rise of temperature during a thaw. 



Mr. Walter Neilson ascribed the fracture of iron in both instances to 

 the efi'ect of contraction. 



Mr. Crum referred to an example where fracture had taken place 

 without any change of temperature, and was probably caused by irre- 

 gular annealing and unequal tension. 



