The Victorian naturalist . ger (1969) added to the theory ofpebbles by defining the fractional de-parture, D, between the apical lineT and the bisectrix as D = — where T isB the maximum distance between theapical line and the bisectrix and B isthe maximum width of the pebble inthe profile being considered. If D isless than , the pebble is regardedas symmetrical, S type. If D is greaterthan , the pebble is type if the bisectrix does not cutthe apical line (Fig. 2), or disym-metrical, Ds type if the bisectrix cutsthe apical line at least once (Fig. 3). Thus the As type co
The Victorian naturalist . ger (1969) added to the theory ofpebbles by defining the fractional de-parture, D, between the apical lineT and the bisectrix as D = — where T isB the maximum distance between theapical line and the bisectrix and B isthe maximum width of the pebble inthe profile being considered. If D isless than , the pebble is regardedas symmetrical, S type. If D is greaterthan , the pebble is type if the bisectrix does not cutthe apical line (Fig. 2), or disym-metrical, Ds type if the bisectrix cutsthe apical line at least once (Fig. 3). Thus the As type corresponds withthe beach pebble and the Ds type withthe stream pebble. Method Pebbles were collected for studyfrom Indented Heads, Port Phillip Bay(marine pebbles); Morrisons, Moora-bool River (stream pebbles) and fromSteiglitz. About 100 non-cracked and unspHn-tered pebbles were selected, in sizeabout 3-10 cm longest diameter. Thesev/ere photographed on graph-paper to *22 Mallaluka Avenue, Ocean Grove. Vict. Nat. Vol. 93. BEACH PEBBLE STREAM PEBBLE give the AB profile. On the photo-graphs each apical line and bisectrixwere drawn and the fractional depar-ture then calculated for each pebble. Results The table shows the results foundfor pebbles from Indented Heads andthe Moorabool River. It was found that As type pebbleswere dominant in the marine sampleand the Ds type in the river neither case were the S type pebbles very common. This is the same resultas Lenk-Chevitch found. As it is possible to check upon theorigin of pebble shape it becomes fea-sible to use this fact in palaeo-eco-logical studies of sediments wherefossil organisms may not be this in mind pebbles were col-lected and measured from a gravel pitat Steiglitz. As shown in the table,the percentage of each pebble typepresent at Steiglitz bears a closer re-semblance to those of the river-wornthan to the ocean-worn pebbles. So wecan conclude that the gravels aboutSteiglitz are river deposits. T
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Keywords: ., bookcentury1800, bookdec, booksubjectnaturalhistory, bookyear1884
