402 Prof. T. G. Bonney. On the [Nov. 27, 



have emitted fire and ejected ashes ; and that it. lies to the east-north- 

 east of Quito, at the distance of more than 40 miles. 



" The examination and ascent of this mountain (which is the least 

 in elevation of those which I explored) occupied a greater length of 

 time and gave more labour than any other, excepting Chimborazo. 

 It will be enough to state in these notes that as we proceeded to the 

 cast we travelled out of the volcanic region of the Ecuadorian Andes 

 and entered the older formations, passing through dense vegetation, 

 which for a time entirely obscured the rocks. We encamped several 

 <l:ivs under the first rock that we came across a large projecting 

 cliff of mica-schist, situated almost exactly upon the Equator, at the 

 height of 12,000 feet above the sea, which bears the name Corrector 

 M<icJiai : and waiting until we could see Sara-urcu, which was almost 

 perpetually enveloped in clouds, reached the summit at length on 

 April 17, 1880. There was a rudely level ridge of some length at 

 the summit, upoii which a considerable amount of rock in situ was 

 exposed, which left no doubfc as to the nature of this mountain. 

 The glaciers we traversed on the west of the peak possessed small 

 but very distinct moraines, and from the moraine matter, which 

 evidently had been borne from various rocks cropping up through 

 the ice, I collected various other specimens of mica schists and 

 quartz, but could not detect a single fragment of the characteristic 

 rocks which you have described in connexion with the other moun- 

 tains the active and extinct volcanoes of the Equator." (E. W.) 



The specimen fi-om Corrector Machai is a rude flat slab of rock which, 

 inacroscopically, most resembles a rather fine-grained micaceous gneiss. 

 The slaty formation is evidently due to a rough cleavage traversing 

 the rock, on he planes of which a silvery mica has been rather largely 

 developed. Under the microscope the specimen is seen to contain the 

 following minerals: A silvery mica in scales, up to '03 inch long, 

 probably a hydrous alkaline-mica; a dull green mica (or, perhaps, in 

 some cases a chlorite), much less abundant ; numerous granules of 

 quartz, with rather even sides and rectilinear outline, a colourless 

 mineral, sometimes rather dusty-looking from included granules of 

 opacite. This appears to have two not very well marked cleavages 

 (indicated often rather by a constancy in the direction of included 

 mica-microliths), which gives with crossing Nicols rather "stronger" 

 colours than quartz (to which it bears considerable resemblance). It is 

 difficult to decide upon the true nature of this mineral andalnsite 

 and kyanite are the two which suggest themselves and as I can get 

 no evidence of its being orthorhombic, I think it more probably a not 

 v-jry characteristic variety of the latter ; there is apparently at one 

 end of the slide a portion of a vein of a similar mineral in a less 

 pure condition ; the long-bladed crystals, so often characteristic of 

 kyanite, do not occur. The structure also of the rock is perplexing; 



