2i8 THE POPULAR SCIENCE MONTHLY. 



may help his understanding of that which is to come. If not 

 provided with maps, etc., we had better go at once to London 

 and provide ourselves at Stanford's. While in London we must 

 not fail to visit the Museum of Practical Geology in Jermyn 

 Street, which issues a number of catalogues of permanent value 

 (33), and a geological guide to London, and contains models and 

 collections of all kinds. Every one will admire the polished 

 marbles, granites, and serpentines. If we have a Saturday free, 

 an excursion of the Geologists' Association may attract us. At 

 any rate, we shall notice that London lies in a geological basin, 

 and, if our drinking-water is from some deep artesian well, we 

 may thank our stars that London has such a favored situation 

 as not to be entirely dependent for water-supply upon the filthy 

 Thames. Let us go north. There are three main lines of tourist 

 travel. The most westerly passes by the lake district of West- 

 moreland and Cumberland. It is curious to note how uniformly 

 that combination of mountain and lake which is most attractive 

 for summer resort occurs where a region of metamorphic rocks 

 has been subjected to glacial action. Lake Superior and Win- 

 dermere, Maine and Switzerland, all answer to this description. 

 We dare not stop to discuss the reasons. (See 4, chapter xxvii ; 

 10, p. 516.) We shall see the same sort of thing in the Trossachs 

 and Switzerland. If you want to do any detailed work in the 

 region, start in from Keswick, where a museiim contains local 

 collections and models. 



Scotch surface geology is of the same glaciated type so fa- 

 miliar in America, and those who wish to study the parallel 

 roads of Lochaber, or the Tertiary gabbros of Judd, must turn 

 to the Scotch survey for guidance (3, 5, 13). For us an excursion 

 or two about Edinburgh must sufiice. The collections of the 

 Museum of Science and Art are fine, and we can climb the vol- 

 canic crags of Castle Hill, Calton Hill, or Arthur's Seat, and 

 wonder what the landscape was like when hot lava rolled down 

 Salisbury crags. At Newhaven, near by, on the shore of the 

 Firth of Forth, the clay ironstone is exposed, and, breaking open 

 the oblong pebbles, you may find a fish, but more likely a copro- 

 lite or septarium. If you wish to see more of the Carboniferous 

 and the coal and iron industry, you have only to run down to 

 Gilmerton, near which are numerous coal-mines, and great piles 

 of iron-ore a-roasting. Ganoid scales and teeth are not rare, and 

 are collected by some workmen. The name of one was Joseph 

 Blair, of Loamhead. 



On our way south again we shall probably pass through the 

 Peak of Derbyshire and behold the scenery of the subcarbon- 

 iferous, the great mountain limestone in its most beautiful de- 

 velopment, its dewy dells, its steep yet rounded bluffs, and its 



