>6z REMINISCENCES OF 



the north bank of the stream, these limestones had 

 been excavated by means of subterranean workings 

 for a great number of years. Geologically they were 

 known by the name of Ardwick limestones. The 

 -question of the age and geological position of these 

 strata had never been satisfactorily determined, but 

 Dr. William Henry was supposed to have settled 

 the points when he announced that the rock con- 

 tained some seven per cent, of magnesia. This deter- 

 mination, coming from a chemist of high reputation, 

 and who was also the inventor of the then cele- 

 brated preparation of calcined magnesia, was regarded 

 as a proof that the Ardwick limestones were the 

 equivalents of the magnesian limestones of Durham. 

 A short time previously the late Mr. Binney and 

 Mr. John Leigh, subsequently officer of health to the 

 Manchester Corporation, had discovered some thin 

 fossiliferous red shales and limestones in the sides 

 of a drain near the banks of the river Irk, at Colly- 

 hurst. It so happened that their paper announcing 

 this discovery was read at the first meeting of the 

 Literary and Philosophical Society that I was able 

 to attend. The two authors were in doubt respect- 

 ing the stratum indicated by these fossils. But I, 

 on examining the specimens on the table with which 

 they illustrated their paper, recognised their identity 

 with some of the most characteristic fossils of the true 

 Durham magnesian limestone. The most important 

 of these fossils was "Aximus obscurus," subse- 

 quently known as " Schizodus obscurus." 



