THE VICTORIAN NATURALIST. 173 



EXCURSION TO BURNLEY. 

 The excursion to Messrs. Willis Brothers' quarry at Burnley, on 

 Saturday, iith March, was attended by eighteen members and 

 visitors. On the road to the quarry a halt was made on the high 

 ground by the engine shed to draw attention to the physical features 

 of the surrounding country, the distribution of the newer basalt, 

 its direction of flow, and the nature of the lava. The remarks 

 were illustrated by a section taken across country from 

 south to north, passing through Richmond. The changes which 

 have taken place since the basalt was first poured out over 

 this spot are considerable, for the old river bed and swamps now 

 lie about 35 feet below the present bed of the Yarra. Tliis 

 depression may have been a direct consequence of the inflowing 

 of the lava stream, which is here piled up to the great thickness 

 of 90 feet. Resting on a floor of river silt, the basalt at this locality 

 appears to show at least two distinct periods of eruption, marked 

 by differences in the structure of the basalt, both in its megascopic 

 and microscopic aspects. In contact with the silt at the 

 quarry base, the basalt is vesicular, which fact is probably 

 connected with the presence of moisture at the time of contact 

 in the area covered by the lava. This vesicular structure is lost 

 after the first foot or two, when the basalt assumes the dense 

 character of a typical bluestone. There is something like an 

 average thickness of 50 feet of rocks of this nature, followed by 

 about 40 feet of easily decomposing basalt showing spheroidal 

 or bomboidal weathering to the top of the quarry. These two 

 beds are irregularly separated by thin and intermittent layers of 

 an ochreous rock, wliich, on closer examination, has proved to 

 be a finely granular calcareous deposit similar to certain travertin 

 tufas met with elsewhere, which are of lacustrine origin ; the 

 calcareous grains each contain a ferruginous nucleus, and they 

 are bound together by crystalline calcite. The descent to the 

 floor of the quarry was made by the nearest path, which proved 

 precipitously steep, and ended in an expeditious reunion at the 

 foot. The party assembled in the N.E. end of the quarry. On 

 the N.E., E., and S. sides the quarry face shows a radial 

 arrangement of slender and somewhat irregular columns, 

 probably induced by the infilling of a valley with sloping sides, 

 since it seems a general rule, as Lyell points out. that the 

 columnar structure is developed at right angles to the cooling 

 surface. On the other hand, Scrope held the view that this radial 

 arrangement is merely due to clots or masses of lava cooled 

 unequally in relation to the surrounding material. 



In two places tree stumps were found here, under the basalt 

 and embedded in the silt, in the east and north-west corners of 

 the quarry. A portion of one of these trunks, which microscopic 

 examination shows to belong to the Coast or Drooping She-oak, 

 Casuarina siricta or quadrivalvis, was fortunately found by the 



