120 LORD HOWE ISLAND. 



George's Sound,* and so does Jukes, t who believed them to be sand 

 stalactites only ; Capt. ~R. J. Nelson, at the Bahamas ; J and the Eev. J. E. 

 Tenison Woods, in the sand dunes of the South Australian coast. § The 

 last-named observer combats the arboreal origin of such cavities in the sand 

 examined by him. 



Whether the phenomena described by Mr. Fitzgerald are due to the decay 

 of trees entombed, or are analagous to those pipes, which frequently traverse 

 chalk and other similar formations, it is impossible to say without a direct 

 examination. 



Guano deposit. — The only exposed outcrop of this observed by myself was 

 at the landing-place, at the northern end of the Lagoon. It forms a bed 

 from ten to fifteen feet thick, and extends along the beach, a little above and 

 between water marks for perhaps thirty yards. Mr. H. T. Wilkinson remarks, 

 " At a point about 20 chains north of Thompson's Point, and cropping out 

 on to the beach is a considerable deposit, consisting of calcareous earth 

 mixed with bird's bones." It is traceable inland, having been proved in 

 sinking wells, but probably occupies only a limited area. No doubt, after 

 the final deposition and upheaval of the Coral-sand rock, the narrow neck of 

 land between the landing place on the west and Ned's Beach on the east, and 

 uniting the North Ridge with the central portion of the island, was occupied 

 by a shallow gut-way. Mr. Wilkinson speaks of a well thirty chains (660 

 yds.) inland, in which this deposit was sixteen feet thick. 



This old well exists in Mr. Thompson's garden, and, through the courtesy 

 of Mr. H. T. Wilkinson, I am able to give the following particulars : — 



Sand... ... ... .. ... ... :.. 4 feet. 



Yellow clay .. . ... ... ... ... ... 14 „ 



Coral sand, passing into " a kind of thick putty 

 mud " of unknown thickness. || 



Speaking of these wells, Mr. E. S. Hill remarks — " In sinking, occasionally 

 argillaceous beds of fourteen feet in thickness have been cut through ; these 

 have been resting on a coral debris, and will retain no water." 



The position of this deposit is not well defined by any boundaries, but it 

 may occupy the whole of the low ground between the foot of the North Peak 

 Ridge on the north, the Landing Place, and Ned's Beach, east and west ; 

 tailing off towards Thompson's house towards the south. That such is 

 the case is probable from further remarks of Mr. Hill's on another well 

 in this neighbourhood, which "was dug nearly through the clay," to a depth 

 of thirty feet. The situation chosen happened to be a kind of basin in which 

 heavy rains collected and there remained till evaporation or percolation 

 relieved the surface. If my supposition relative to the depression is correct, 

 then the so-called " G-uano " was deposited on its flanks, and insensibly 

 graduates laterally into the superincumbent layer of loam. 



The thickness, I was informed, has been proved to thirty feet, and it does 

 not probably extend to a much greater depth beyond this. The deposit is 

 frequently spoken of as the " Guano " ; by Mr. Wilkinson it is called 

 " calcareous earth mixed with bird's bones." For my own part, the deposit 

 appeared to possess a much higher argillaceous than calcareous nature. 



* Geol. Obs. Vole. Islands, 1844, p. 745. 

 + Quart. Journ. Geol. Soc. 1853, ix, p. 211. 

 + Phys. Structure of Australia, 1850, p. 61. 

 § Geol. Obs. S. Australia, 1862, p. 167. 



|| The well could not be sunk lower on account of water, which stands at 18 in., and is 

 not diminished or increased by pumping, or rain. 



