160 MK. W. S. BOULTOX ON THE [May I904, 



agglomerate, with lapilli and bombs of basalt and lumps of lime- 

 stone ; while, for the remaining 100 yards or so, it is an ordinary 

 basalt- coulee, with very few, and always small, lumps of burnt 

 limestone. 



III. Relation of the Basalt to the Limestone below it. 



The basalt rests upon a hard bed of pink limestone, about 9 feet 

 thick. Immediately under the basalt the red coloration is intense, 

 but passes down into reddish-yellow and yellow; and the limestone, 

 especially in its upper portion, is markedly crystalline to the naked 

 eye. Below this bed is the typical, purplish-brown, fossiliferous 

 limestone about 25 feet thick ; and this again is underlain by a soft, 

 pink, nodular rock, showing oblique lamination, and containing the 

 remains of corals and encrinites. This last bed is somewhat tuffy- 

 looking, but an examination of the residue, after treatment with 

 boiling hydrochloric acid, shows that it is an excessively-fine 

 red mud, without any recognizable volcanic lapilli, but probably 

 derived from some volcanic centre. This residue is in striking 

 contrast with those from the calcareous tuffs at Middle Hope, all of 

 which show abundant lapilli of basalt-glass, felspar-crystals, etc. 



Sir Archibald Geikie & Mr. Strahan tabulate the following 

 succession of these rocks at Spring Cove {op. cit. p. 105) : — 



' Massive limestone, full of fossils. The lowest 3 feet of the rock are crowded 

 with fine volcanic dust, which, under the microscope, is seen to consist of fine 

 vesicular lapilli. 



' Highly-amygdaloidal altered basalt, having a " pillow "-structure, and with 

 abundant calcareous and haematitic veins, and threads of carbonate of copper ; 

 about 35 or 40 feet. 



' Red* limestone, full of fine volcanic dust, and passing down into the 

 ordinary grey, fossiliferous limestone.' 



Iii the limestone under the basalt I have been unable to detect 

 any undoubted igneous fragments, of the nature of volcanic dust or 

 lapilli (despite a diligent search in thin slices under the micro- 

 scrope), from the basalt-junction down to a depth of 9 feet in the 

 limestone. But the soft red rock, some 35 feet below the basalt, 

 may represent, as stated above, very fine volcanic dust, while a 

 section of the reddish-purple limestone, 8 feet below the basalt [23], x 

 has a very tuffy appearance, as remarked below. 



The following is a description of some of the sections cut from 

 this underlying limestone : — 



[3] Reddish limestone, in contact with the basalt. The slice 

 clearly shows elliptical and rounded oolitic grains, set in a matrix 

 of calcite, occurring in small, irregularly-outlined crystals, and 

 with well-marked cleavage. As the rock approaches the junction 

 with the basalt, the oolitic structure gradually disappears, and the 

 rock comes to consist of a confused aggregate of minute calcite- 



The numerals in square brackets, throughout this paper, refer to the 

 numbers of the slides in the Author's ' Weston collection,' 



