284 Correspondence — Dr. C. Callaicay. 



and of the fault inferred from the seismic evidence is so close, that 

 tliere can belittle doubt that the earthquake was due to a slip along 

 this fault. 



The nature of the shock, the sound-phenomena, time-relations, 

 and after-shocks are described in detail, and some account is added 

 of the earthquakes of 1890 and of sympathetic earthquakes in the 

 valley of the Findhorn. There were two distinct slips in rapid 

 succession, with continuous slight motion between them, the second 

 being greater in amount and extending over an area which probably 

 overlapped, even if it did not entirely include, that within which, 

 the first took place. The great slip reached nearly from Loch Ness 

 to Inverness, and was greatest at a point about half-way between. 

 The three chief after-slips resulted in an extension of this area in 

 both directions along the fault-surface, the extension to the north- 

 east being small, while that to the south-west amounted to 6 miles 

 or more. In addition to this migration of the focus, there was also 

 a continuous decrease in the depth of the focus. The earthquakes 

 provide no evidence with regard to the direction of displacement 

 along the boundary fault. There can be little doubt, however, that 

 Loch Ness is still growing ; but it can hardly be determined 

 whether the lake is now contracting in area, or whether it is 

 gradually pushing its way outward to the sea. 



3. ''The Wood's Point Dyke, Victoria (Australia)." By Frederic 

 Philip Mennell, Esq., F.G.S. 



This dyke is intrusive into a belt of Silurian (Upper Silurian) 

 strata whicli strike in a direction somewhat west of north, and 

 extend beyond Walhalla on the south. Wood's Point is about 

 75 miles east of Melbourne. It may be taken as typical of the 

 intrusions associated with the Silurian rocks of the Victorian gold- 

 fields. Brown, original hornblende is the dominant constituent, 

 but it is rarely idiomorphic ; augite, three varieties of felspar, 

 micropegmatite, and ilraenite are also present in a microcrystalline 

 or cryptocrystalline groundmass. The rock is called a hornblende- 

 porphyrite. In certain varieties cordierite occurs, and is accounted 

 for by derivation from the adjacent shales. The reefs in the Silurian 

 and Ordovician rocks usually occur at or near the contact with 

 intrusive rocks. At Wood's Point the reefs are nearly horizontal, 

 traversing dykes and shales, the junction usually marking the 

 occurrence of rich ore. The author notes the " almost invariable 

 association of gold in this class of deposit with rocks containing 

 original hornblende." 



C0I^K,Es:E502^^IDElI^^G:E]. 



THE CRYSTALLINE LIMESTONES OF CEYLON. 

 Sir, — As one of the unfortunates who are unable to attend the 

 meetings of the Geological Society, I crave permission to make 

 a comment on the interesting paper on "The Crystalline Limestones 

 of Ceylon "read on the 12th March by Mr. AnandaK.Coom;ira-Swamy. 

 The author and all his critics profess themselves more or less puzzled 



