554 F. Chapman — On Concretionary Nodules. 



not the main bed of the river, but a neighbouring backwater, 

 occasionally subjected to tidal influences. 



On the sides of tlie valley sloping to the old river channel at 

 S. Melbourne, several flattened nodules, circular in outline, veere 

 found embedded in silt, and in close proximity to the clay bottom. 

 The angle of slope of the sides of the channel at this spot was about 

 2° (1 in 30). Externally, these nodules have the appearance of 

 flattened balls of clay, mixed throughout with small fragments of 

 dark-brown lignitoid plant-remains and fragments of charred wood.' 

 On splitting open some of the nodules, which easily separate, 

 sometimes along the median (equatorial) plane, or in parallel cakes, 

 there is revealed a moderately thick layer, almost entirely composed 

 of matted fragments of woody and foliaceous material, around and 

 amongst which the clay, permeated with a large amount of carbonate 



Fig. 1. — Cleaved surface of nodule from the old bed of the Yarra at S. Melbourne, 

 showing included fragments of wood. (One-half the diameter of original.) 



Fig. 2. — Convex outer surface of the same nodule, showing small fragments of charred 

 wood. (Reduced one-half.) 



of lime, seems to have accumulated. The calcareous nature of 

 these nodules is shown by the strong efi"ervescence on treatment 

 with HCl. 



A little of the outer crust of the nodule was taken for examination 

 under the microscope, when it was seen to consist of quartz-grains, 

 fine calcareous and argillaceous particles, brown woody tissue, and 

 valves of the marine diatom Actinocychis. 



The residue of the powder from the nodule, after treatment with 

 H CI, showed it to consist largely of a fine angular quartz sand, the 

 grains of which have a diameter varying generally between •! mm. 



' Mr. Spry has also shown me portions of brandies of gum-trees, one of which has 

 been charred by lire. These he found at the bottom of a sewer manhole at the corner 

 of McGowan and Povrer Streets, at 14 feet from the surface and alH)ut 4 to 6 feet 

 below the present low-water mark. Prehistoric bush-tiies must have been of frequent 

 occurrence, and maybe ascribed to the action of lightning. At the time of writing 

 this note there is a paragraph in the Argus, February l4th, 1906, reporting several 

 bush-fires having been started by lightning at Chetwyiid aud Kadnook in Western 

 Victoria. An interesting feature connected with the above occurrence of drifted wood 

 was a bank of marine shells 7 inches thick, left behind the logs by the retreating tide. 

 See also the reference to charred wood in coal-seam nodules by A. C. Seward (" Fossil 

 Plants," vol. i, p. 88). 



