33 



found to give not the sliglitest trace of organic remains — not 

 even so mncli as a f oraminif er — although the material was care- 

 fully washed and searched under the microscope. Moreover, in 

 the clay, especially in the upper portions, the sand proper to 

 the bed is extremely fine and sharp mixed with flakes of mica, 

 whilst the sand in the fossiliferous pipes is comparatively 

 coarse and similar to the beach sand which overlies the clay. 

 [From the considerations just set forth it seems a moral certainty 

 that the deposition of the fine, sandy, non-fossiliferous clay 

 was not synchronous with the coarser sand and shells which are 

 included in vertical lines in the upper three feet of the bed, but 

 that the latter is of distinct origin and subsequent date. There 

 appears but one theory capable of explaining the matter. The 

 bed in question, prior to the deposition of the littoral sands 

 now overlying it, must have been at the surface and subject to 

 the desiccating influence of the sun and atmosphere, by which 

 the surface became cracked, much in the way that the clay 

 ground of the marshes around the Port Creek is rent now in 

 the hot season. When in this condition, the sea came in, 

 bringing its drift of sand and shells, which immediately filled 

 up the fissures in the clay, and in this way placed in vertical 

 juxtaposition material of somewhat different geological age. 



JVos. 6 and 7. The next bed in descending order is a cal- 

 careous sand, very rich in fossils, and is about four feet in 

 thickness. This bed is generally loose and friable in its 

 character, but is coated on its upper surface with a " limestone 

 crust," the latter supplying so excellent a floor line for the 

 proposed dock that *Mr. Eietcher decided to make it the base of 

 the excavations, instead of going a foot deeper, as was intended 

 according to the plans. This limestone crust is a somewhat 

 remarkable and suggestive feature. Whilst the bed with which 

 it is associated is highly fossiliferous, this crust is non-fossil- 

 iferous, and is evidently a travertine, and must have been formed 

 whilst the bed in question was above water and exposed to 

 meteorological conditions. Prof. Tate some years ago showed 

 that the limestone crusts, which form over the calcareous lands 

 in this colony, are the result of evaporation of water charged 

 with the carbonates of calcium and magnesia causing these 

 minerals to aggregate at or near the surface of the ground. If 

 so, then the travertine on the top of the calcareous bed now 

 under consideration, and which is 191 ft. below present low- 

 water mark, must have been at the surface and dry land sub- 

 ject to the solar rays before the travertine could have been 

 formed. This crust has been but slightly disturbed, so that I 



* Since the above was writteu Mr. Fletcher has informei me that he in- 

 tends carrying out the original design as to depth. 



