:^4 THE BUILDING OF AN ISLAND. 



formation of the dvke. The ahove examples of dykes may be sufficient to 

 illustrate their character, the student will readily find others; but besides 

 appearing in the form of dvkes, the igneous rocks appear sometimes to have 

 been thrust up in considerable masses. The rocks at the summit of Mt. Eagle 

 appear to be of this kind.'*" At the cattle pen at the estate " Bugby Hole," a 

 great mass of cream-coloured rock, inclining to red, may be seen, which appears 

 to be the same rock as is so abundant along the south side of St. Thomas and 

 is called by Professor Cleve felsite. Around the works and the residence at 

 the estate Annaly, a rock appears which weathers to a white clav and, conse- 

 quently, has in some parts the outward appearance of a marl. It is a massive 

 unstratified rock of a verv pale green colour and has a semi-translucent appear- 

 ance. It is presumably a felsite. 



At the bank by the side of the high-road at " Grange " and also on part of 

 the estate " Beeston Hill," there is a highly decomposed igneous rock which 

 contains a quantity of yellow mica in shining specks. A similar rock is found 

 at the estate " Hermitage." The mica is probably coloured by a trace of gold, 

 at all events the writer was shown, many years ago, a sample of yellow^ mica 

 sand which had been sent from St. Croix to London for expert opinion, and 

 which was reported on as containing gold, but not in any payable quantity. 



Among the stratified rocks which are seen on " Blue Mountain, "t an 

 igneous rock has forced its way, and near to the summit of the mountain has 

 partly broken up the strata so that the fragments of these are seen embedded 

 in the intruded rock. This rock is fine-grained, grey in colour, and externally 

 resembles grey granite. It probably belongs to the same class of rocks as that 

 mentioned in the following paragraphs. 



* The following notes were made by the present writer after ascending to the summit of this hill : 

 " Ascended from ' Hermitage ' to lower part of the ridge and then proceeded northwest and after- 

 wards west to the summit of Mt. Eagle. The whole slope of the ridge is covered with loose blocks and 

 smaller pieces of stone. Most of these show clear traces of stratification in narrow brown and whitish 

 brown bands. Mingled with these there are, however, many pieces of igneous rock, characterized by 

 numerous and rather large felspar crystals [probably felspar-porphyry]. The summit of Mt. Eagle shows 

 no stratification, but appears to be a compact or very fine-grained crystalline rock of igneous origin. The 

 rock is split by numerous cracks [joints], for the most part vertical and having the direction of east and 

 west." 



t The following notes were made by the writer after ascending the ridge, as mentioned in the pre- 

 ceding note -. 



" Passed along the ridge [Mt. Eagle Ridge] to Blue Mountain. Ascending towards the summit 

 found traces of stratification on the way up, dip east-southeast, at a high angle [70 to 75 degrees]. At 

 summit found same dip continued. The rocks here are in bands of a brown, whitish brown and light-blue 

 or slate colour. In one part the rocks appear to have been entered by greenstone and the strata seem to 

 have been broken up by it and the pieces mi.^ed with it. The greenstone is very fine-grained and is 

 e.^ternally grey. The stratified bands are mostly very thin and recall the rocks at ' Buck Island' and 

 some of those about ' Judith's Fancy '. 



" Near the summit \oi Blue Mountain] on the northeast there is a protrusion of greenstone which 

 weathers light grey and looks much like grey granite. It is split by joints running north-northeast and 

 south-southwest at a high angle and by others at right angles. These joints are so regular that it is diffi- 

 cult to resist the impression that the rock is regularly stratified, yet the crystalline structure is perfect and 

 the composition of the two or three layjrs exposed seems to be identical. It is probably an intrusive sheet 

 of greenstone. This rock exhibits some beautiful hornblende crystals on the exposed surface." 



