88 A. Heard — TJie Petrology of tlie Pennant Series. 



a number of fruitless experiments, advantage was taken of the fact 

 that a potash-alum solution dissolves calcite. Control experiments 

 were carried out with calcite and siderite. Calcite proved to be 

 soluble in a cold alum solution ; siderite was insoluble, even after 

 boiling and standing for forty hours. Hence it was concluded that 

 an alum solution would dissolve the calcium carbonate from the 

 original rock, and leave the iron carbonate — if present — behind. 



A small quantity of the powdered sandstone was heated in an alum 

 solution ; an evolution of carbon dioxide began, thus demonstrating 

 the presence of calcite. The solution, after being left for a day, was 

 filtered and tested for iron, but none had been taken up from the 

 rock. The residue was treated with dilute hydrochloric acid ; an 

 evolution of gas commenced, and the solution on testing revealed 

 a relatively large proportion of iron. Attempts were made 

 to estimate quantitatively the amount of calcium carbonate by this 

 method ; the average percentage was 2-2"3. Quantitative chemical 

 analyses gave about 0"9 per cent calcium = 2"2 per cent calcium 

 carbonate, thus demonstrating the fact that practically all the 

 calcium carbonate had been removed by the alum solution. 



Effects on Ignition. 

 The air-dried, powdered Pennant Sandstone was a greyish white 

 before ignition. After ignition in an open crucible the powder 

 changed to a pale salmon colour, forming a vivid contrast when 

 placed side by side with the original powder. This change in colour 

 was attributed to the calcination of the iron carbonate in the cement. 

 The effects of ignition were still more strikingly demonstrated when 

 the quartz grains from the original rock were mounted with grains 

 from a sample which had been ignited and viewed under the micro- 

 scope in reflected light. The former were clear, while the ignited 

 grains were coated with a pellicle of iron oxide. Hence it was con- 

 cluded that iron carbonate was present in the cement in relatively 

 large quantity, in addition to calcite, secondary quartz, and 

 carbonaceous material. 



The Carbonaceous Material. 

 Carbonaceous matter was scattered throughout the rock in varying 

 proportions, and generally in angular form. To eliminate any 

 possibility of this black material being graphite, numerous fragments 

 were placed on zinc and immersed in a copj)er sulj)hate solution. 

 When placed under the microscope no coating of coj)per on the zinc 

 was observed, and it was concluded that no graphite was present. 

 Grains were treated with nitric acid and potassium chlorate, and then 

 with ammonia. When mounted a few of these fragments yielded 

 clear indications of plant structure. Portions of cuticle enveloping 

 nodular masses were found. These may have been spore-cases ; 

 but were not so well defined as to be determined with certainty. 

 Excellently well preserved specimens of woody tissue were present ; 

 the walls were relatively thick, and showed no signs of pitting, etc. 



