108 Dinhur Castle, its Gardens and Gardeners. 



man : but, however varied and beautiful the exterior features of 

 the earth may be, together with the herbs and trees that adorn 

 it, and the numerous tribes of organised beings which people it, 

 yet the interior structure of our earth deserves also our parti- 

 cular attention ; for it could be easily shown how close a relation 

 exists between rocks and soils, and how a knowledge of the na- 

 ture of soils must be of essential benefit to those who cultivate 

 them ; eveiy gardener, therefore, ought to be a geologist. 



Walter Glenesk took his own way to illustrate his subject. 

 When travelling from place to place, he made himself, as far as 

 he was able, familiar with the geological features of the coun- 

 try through which he passed, and when he had settled he col- 

 lected specimens of the rocks and erratic boulders which he 

 found in the neighbourhood of the place in which he resided, so 

 he was enabled to make his discourse more interesting, by exhi- 

 biting specimens of many of the rocks that form j^art of the dif- 

 ferent geological formations. The other lads in the bothy were 

 able to examine the specimens at their leisure, which was an ad- 

 vantage which many students who attend geological lectures do 

 not enjoy. He had prepared an ideal section of part of the 

 earth's crust on a large scale, by means of which he was able to 

 point out more clearly the relation which one rock bears to 

 another. 



He commenced with granite, a rock considered as occupy- 

 ing the lowest part of the series, and often found in moun- 

 tain ranges at the highest elevation. He did not stop to tell 

 them of its constituent parts, but went on from granite to 

 gneiss, from gneiss to mica-slate, from that to chlorite-slate, talc- 

 slate, hornblende-slate, clay-slate, primary limestone, quartz 

 rocks, and serpentine rocks. Having gone over the various 

 rocks of the primary formation several times, until the others 

 could name them in their order, he then proceeded in describing 

 the constituent parts of granite. He told them that it was com- 

 posed of felspar, quartz, mica, and sometimes hornblende, but 

 they were not to imagine that these were simple substances ; 

 and, taking up a specimen of felspar, he told them that it was 

 composed of potash, silica, and alumina ; mica contained potash, 

 silica, alumina, magnesia, and iron ; hornblende was composed 

 of silica, lime, iron, and magnesia ; and quartz, when pure, 

 consisted of silica alone. He then showed them the difference 

 between the best Aberdeen granite and that of Peterhead and 

 Braemar: how it varied in colour; sometimes it was flesh- 

 coloured, at other times dark grey : how some kinds of it were 

 indestrvictible, and others were easily decomposed by means of 

 the air and water acting upon the potash of the felspar. The 

 celebrated Cornish clay, much used in potteries, is obtained from 

 decomposed granite ; and sometimes, when the clay is mixed with 



