CHAMBERS'S INFORMATION FOR THE PEOPLE. 



Stonehaven and Helensburgh. They consist of 

 shales, limestone, graywacke, c. but the series 

 is greatly metamorphosed ; the lower strata being 

 converted into quartzose flagstones and quartz 

 rock, the upper into chlorite and mica-slate, and 

 quartzose and gneissose rocks. Immense tracts 

 of the lower Silurian beds have hitherto proved 

 devoid of fossils ; in other districts, the cal- 

 careous rocks are almost entirely composed of the 

 remains of marine invertebrate animals, while 

 the shales abound in zoophytes and Crustacea, 

 The Old Red Sandstone Strata, consisting of con- 

 glomerates, coarse and fine-grained sandstones, 

 and dark-coloured schists, with the characteristic 

 fossils of ganoid and placoid fish, frequently over- 

 lie the Silurians. Nearly all Caithness, and the 

 seaward portions of Sutherland, Ross, Cromarty, 

 Inverness, Nairn, and Moray, belong to these 

 strata, which also appear in many parts of the 

 east and south-east of Scotland, in South Wales, 

 Devon, and Cornwall, where the predominant 

 rocks are slates, sandstones, and limestones, and 

 the fossils, coral and shell-fish. The strata of the 

 Carboniferous period may be said to occupy a 

 broad but broken tract, extending, in England, 

 from the Bristol Channel to the base of the 

 Cheviots ; and in Scotland, filling the great trough 

 between the Silurian measures on the south, and 

 the Old Red Sandstone on the north. Besides coal, 

 the whole of the Carboniferous series contain im- 

 mense stores of argillaceous carbonate of iron, 

 from the ore of which is produced the great bulk 

 of iron used in the country. The Permian strata, 

 consisting of magnesian limestone and sandstone 

 coloured with oxide of iron, occupy a considerable 

 area in the centre and north of England. Two 

 small tracts of highly fossiliferous Lias occur, the 

 one in Glamorgan, the other in Shropshire ; and 

 small patches exist in Scotland, at Brora in 

 Sutherland, and in the islands of Skye, Eigg, and 

 Mull. Far more extensive and important, how- 

 ever, are the Oolite measures, which form a belt 

 nearly 30 miles broad, from Yorkshire to Dorset- 

 shire, curving round by way of Lincolnshire. The 

 best building material in England is obtained 

 from these strata, which are composed of lime- 

 stones, sandstones, and shales. The fresh-water 

 Wealden series, with their abundant remains of 

 reptiles, fishes, shells, and insects, occur in Kent 

 and Sussex, in the Isle of Wight, and in Devon ; 

 the fossiliferous beds of the Cretaceous period, con- 

 sisting chiefly of chalk, with intercalated sands 

 and clays, lie east of the oolite strata, and parallel 

 to them, and have a historical celebrity in the 

 'cliffs of Dover,' whose w^zte-gleaming heights 

 are supposed by some to have originated the 

 name Albion, which our island once bore. Eocene 

 strata, composed of clays, sands, and marls, occur 

 in various parts of the south and south-east of 

 England ; Pliocene deposits of shelly sand and 

 marl in Suffolk ; and the still more recent Pleisto- 

 cene deposits of fresh-water sand and gravel on 

 the coast from Norfolk to Kent 



CLIMATE. 



It is impossible to contrast the climates of Eng- 

 land and Scqtland generally without misleading, 

 because, for several months in the year, longitude, 

 and not latitude, is the agent which mainly affects 

 the various climates of Great Britain, Thus, the 



242 



annual mean temperature of Greenwich is 3-4 

 higher than that of Edinburgh ; but to know 

 this fact alone is worse than valueless, because 

 July is, on an average, 5 warmer in and near 

 London, while January has the same temperature 

 in both places. From charts prepared by Mr A. 

 Buchan (Scot. Meteorological Society Journal, Nos. 

 28, 29), based generally on the observations of 

 the thirteen years 1857-69, it appears that the 

 lowest line of mean temperature at the level of 

 the sea which touches Great Britain in January, 

 the coldest month, is 37 ; but this only embraces 

 the tract from Kinnaird Head to Aberdeen. 

 The line of 38, again, starting from the Faroe 

 Islands, enters Scotland by the Moray Firth, 

 runs west by Perth, Greenock, Glasgow, and 

 Dumfries, traversing England by Carlisle, Derby, 

 and the Naze ; 39 starting from the Shetland 

 Islands, passes through the Hebrides, the Mull 

 of Kintyre, and Galloway. Hence January in 

 the south-east of England is i colder than in 

 the Shetland Islands and on the whole west coast 

 of Scotland, and as cold as in the Faroe Islands 

 in 62 N. lat In the Hebrides, again, and in 

 the south-west of Scotland, the January tempera- 

 ture corresponds with that of Dublin, Bristol, and 

 Portsmouth. February makes but a slight alter- 

 ation, relatively, in the temperature of Great 

 Britain. In March, latitude begins to supersede 

 longitude as the determining agent. An Edin- 

 burgh March is about equal to that of York, and 

 2 below that of London. April in London is 

 3 warmer than in Edinburgh. It may here 

 be observed that seasons differ less from one 

 another in mean temperature on the west coast 

 of Great Britain, generally, than they do on the 

 east coast ; and that while the winters of the west 

 are warmer, its summer is cooler. But this differ- 

 ence in favour of the west in winter, as compared 

 with the east and inland places, arises chiefly 

 during the night. This fact, Mr Buchan attrib- 

 utes to the great predominance, in winter, of 

 south-west winds, ' which,' he says, ' arrive on our 

 western shores bringing the high temperature of 

 the ocean they have just crossed. At the same 

 time, being cooled by coming in contact with the 

 surface of the earth, at this season many degrees 

 cooler than the Atlantic, their superabundant 

 vapour is condensed into clouds, which partially 

 screen the west coast from those intense colds 

 produced by nocturnal radiation. On the other 

 hand, the south-west winds are rapidly cooled as 

 they proceed northwards, and being drained of 

 much of their moisture, the skies are clearer, 

 and thus less obstruction is offered to radia- 

 tion.' 



From this we infer, that during the prevalence 

 of north and north-east winds, the higher tem- 

 perature of the west coast will be lost, and these 

 winds are just as prevalent in spring on the one 

 coast as on the other. The point is one which 

 deserves the attention of medical men, and those 

 whose health depends on climate. 



The coast of Argyllshire, as might have been 

 expected, has a very high winter temperature. 

 The number of frosty nights which occur there 

 in January, is rather fewer than in May in Upper 

 Deeside, where the Scotch winters are coldest 

 At Easdale in Argyllshire, in January 1862, the 

 temperature never fell to 32 ; and during seven 

 years, 1857-64, twelve nights of frost were the 



