IOO 
Mr. Mills’s Obfervations , &c # 
Vitrefcent fubftance from Ardlun, - - 2 5 8oa 
Toadftone, from great rocks Derbyfliire, yellow grey, 2,133 
dark compadt, 2,634 
ditto cellular, 2,528 
■ yellow grey from Bonfal, 2,219 
i - j 
[Specimens of all thefe fubftances, except the Jet and Cannel 
Coal, accompanied the Paper.] 
EXPLANATION OF THE FIGURES, TAB. IV. 
Fig. l. View of the Glen near Ardlun Head in Mull. 
2. View of the infulated Rock at the termination of the 
Glen. 
3. A view of the great Fiflure, the Cave, and the lufi* 
pended Stones, in the Ifland of Mull. The fiflure 
ranges N. and S., is about ten feet wide and forty 
yards deep : the fides and the fufpended {tones are 
granite. 
