170 Fwceedings of the Royal Society of Victoria. 



The squeezing out of the slate goes so far as sometimes to show 

 only occasional slate patches along a definite line of junction of 

 two other beds. The connection with joints and fractures and 

 contortion sometimes noticed, as well as the irregularity of the 

 occurrence, indicates this as squeezing out, not thinning out. 



The tendency of more plastic beds to thicken in the curves of 

 a highly folded series and to squeeze out from the flanks of 

 the folds is well known. If we look at the ordinary folds of the 

 Ordovician rocks here we will find that a large portion of any 

 bed is approximately a plane between the more sharply curved 

 poi'tions. If we have then a plastic bed whose thickness is 

 comparable with the minor irregularities and small displacements 

 of the more rigid beds alongside, it will be completely squeezed 

 out irregularly, and patches will be left which have no passage 

 by which they can move towards the folds, so that, in the 

 extreme case we should expect a slate bed not to be completely 

 squeezed into the folds, but to be represented by a number of 

 more or less isolated remnants. 



Even if no considerable area of the beds was near a plane, the 

 boundary of the area from which the slate was removed would be 

 irregular, and a section passing anywhere near this boundary 

 would show more or less discontinuity in the slate. 



The squeezing out would not necessarily take place especially 

 at the places where the strata were most steeply inclined. 



Again, the material of the more plastic beds is frequently seen 

 to enter cracks in the adjoining sandstone, and this is most 

 common when the cracks make an angle with the bedding 

 considerably less than a right angle. By the gradual widening 

 of this crack, either by bending of the bed or by the pressure 

 forcing the more plastic material into it, we thus obtain a wedge 

 of slate in a sandstone, and a corresponding wedge of sandstone 

 in the slate. If such a wedge is cut transversely it may appear 

 as an isolated fragment of slate in sandstone near to the main 

 slate bed ; but it may also appear as an isolated sandstone 

 fragment included in slate. Examples of this are seen in 

 various sizes up to that instance at Italian Hill. In an 

 extreme case a considerable portion of a slate bed may appear 

 as isolated fragments. As the irregular folding and yielding 

 of the beds must result in frequent readjustments of the 



