248 



Major A. W. Baird. Report on the [Jan. 31, 



ever, it would seem to be a blacker and compacter rock than any that 

 I have seen, more like some of those from Antisana. 



" Guaguapichincha aus 14,238 Fuss Hohe." Black, pitchstone- 

 like, small albite, green angite, magnetite (glassy andesite). 



Si0 3 67-07 Sp.gr. 2'579 



A1 2 3 13-19 



Fe 2 3 4*74 



Mn 3 3 0-32 



CaO 3-69 



MgO 3'46 



K 3 2-18 



ETa 2 4-90 



Ignition '30 



Ti0 3 trace 



99 -85 



From the above descriptions, it may be, I think, fairly inferred 

 that the main peak or cone of Pichincha consists chiefly of hornblende - 

 andesites, and the second summit (Rucu-Pichincha) of hypersthen- 

 iferous augite-andesites ; and that there is considerable uniformity in 

 the character of the rocks of this volcanic mountain.* Those from 

 Antisana, which it is intended to describe in the next communication, 

 are of a rather more varied nature. 



III. " Report on the Tidal Disturbances caused by the Volcanic 

 Eruptions at Java, August 27 and 28, 1883, and the 

 Propagations of the ' Supertidal ' Waves." By Major A. 

 W. Baird, R.E. Communicated by Lieutenant-General J. 

 T. Walker, R.E., F.R.S., with a letter from the Communi- 

 cator containing an Abstract of the contents of the Paper. 

 Received January 24, 1884. 



(Abstract.) 



At the request of Major A. W. Baird, R.E., I herewith forward for 

 presentation to the Royal Society, a report which he has prepared on 

 the Tidal Disturbances caused by the now famous volcanic eruptions 

 which occurred on the 27th and 28th August last year, in the Island of 

 Krakatoa and the Straits of Sunda, between Sumatra and Java. For 



* I have seen, in collections of rocks from Hungary, specimens bearing con- 

 siderable resemblance to those from Pichincha : for instance, an " amphibol- 

 andesite " from Altsohl is like those of Gnagua-Pichincha, and one from Blanfuss, 

 Kremnitz, like specimens from JSma-urcu and Rucu-Pichincha. 



