I* 



ERRIXA. 



KHVUM. 



lie, and the quarter whence they nem to hare oome, they are very 

 various. We hare just Men that in the north of Mecklenberg the 

 train* are in a line west-north-west and east-south-east Count 

 Rasoumovski observe* that, when many blocki are accumulated they 

 form parallel lines with a direction from north-eait to south-went. 

 Brongniart Bays they hare a general direction north and south. Sir 

 Jamee Hall speak* of those in the neighbourhood of Edinburgh as 

 coming from the west We have said that those on the north of the 

 Alps oome from the south. 



If anything further wen necessary to complicate the problem of 

 Erratic Blocks, it in the immense distance at which they are some- 

 times found from the nearest rocks of similar composition ; th us 

 blocks of granite are found on the mountains of Potosi, while the 

 nearest granite rocks are in Tucuman, about 400 leagues off. Nor 

 is distance all ; the detached blocks are found separated from their 

 parent rocks by intervening hills, broad and deep valleys, as that of 

 the Aar, and even by straits and seas : thus in the north of Cumberland 

 there are boulders which have been transported across the Solway 

 Frith from Dumfries, and the blocks on the low plains of Germany' 

 are separated from their parent rocks by the Baltic. 



England, as well as the continent of Europe, has many spots 

 covered with Erratic Blocks, some of which seem to be derived from 

 Norway, while others are evidently the debris of our own mountains. 

 For details we refer the reader to the observations and works of 

 Sedgwick, Conybeare, Lyell, Bucklaud, Phillip!!, Hibbert, &c. 



Erratic Blocks are also common in America and other parts of the 

 world. 



From what has been already said, and from the circumstance of 

 Erratic Blocks lying on some of the most modern formations, it will 

 be easily conceived that they present one of the most inexplicable of 

 geological phenomena. The blocks on the Jura, and from the Alps 

 generally, having first attracted notice, have given rise to a great 

 variety of hypotheses, the most remarkable of which are the follow- 

 ing : 1. De Luc was of opinion that these blocks had been projected 

 into the air by the same force which upheaved the Alps, and that 

 they had fallen at greater or lesser distances, according to the strength 

 and direction of that force. 2. Von Buch, Escher, &c., attribute 

 their existence to an immense debacle which swept down the blocks 

 from the Alps to the foot of the Jura, up the slope of which they 

 were forced by the impulse they had received, in the same way as a 

 ball rolled along with force rises up a hillock. 3. Others, as Daubuis- 

 son, have thought that these blocks, which are almost wholly of 

 transition rocks, were the remains of a mantle of these rocks, of later 

 formation than the limestone of the Jura, and consequently much 

 more recent than is generally admitted, and which, having been 

 destroyed, left nothing but these testimonials of their former exist- 

 ence. 4. Dolomieu supposed that the summits of the Alps were 

 formerly connected with those of the Jura by an inclined plnue, which 

 has been destroyed by the same revolution that precipitated the 

 blocks from the summit of the Alps to the plateau, and into the 

 valleys of the Jura. 5. Venturi has attempted to explain the passage 

 of the blocks from the Alps into the basin of the Po, by floating 

 them down on rafts of ice. 6. Others have upheaved the Jura, which 

 they suppose to have been formerly on a level with the base of the 

 Alps, and with it the blocks which hod rolled down upon this 

 calcareous plain. 7. Finally, Von Buch, extending his general theory 

 to the particular phenomenon, thinks that the dispersion of the 

 blocks is the result of an upraising of the Alps posterior to the 

 formation of the tertiary rocks. 



M. Brongniart very justly observe* that these hypotheses leave 

 many difficulties unexplained : he conceives that as the phenomenon 

 of Erratic Blocks is a very general one, it is presumable that the 

 cause also is general. Certain it is that even if it were possible 

 satisfactorily to assign a cause for the Erratic Blocks found upon the 

 Jura, the same reasoning would hardly be applicable to other cases ; 

 and in the utter impossibility of discovering any single cause com- 

 petent to the production of such different effects, wo must have 

 recourse to the more probable conjecture of M. Lariviere, that the 

 dispersion and disposition of Erratic Blocks have been effected in 

 different ways. The more powerful cause however he conceives to 

 be the transporting power of icemeers and icebergs, in which opinion 

 be is followed by Mr. Lyell and others. 



Erratic Blocks, like other phenomena, are attended with tin ir 

 peculiar advantages : thus on hot and dry soils, and when not in too 

 great abundance, they keep the soil cool and moist, sheltering it from 

 the direct rays of the sun in the day, and thus diminishing the 

 evaporation of ita moisture. On cold soils they tend to maintain an 

 equable warmth by diminishing radiation at night. Income countries 

 they are the only building-stones, as in East Friesland and the 

 neighbourhood of Groningen. In others they supply the necessary 

 lime, as at Konigsberg, Revel, fee. Those of a convenient sue are 

 used in Russia and Poland for paving the towns : when broken they 

 are exceedingly well adapted for the repairs of roads. 



IUUNA. [MlLLITORIDAl 



ERU'CA, a genus of Plants belonging to the natural order Cruci/era, 

 and to the tribe Brauicta. It has an erect calyx, obovate petals, 

 distinct, not toothed stamens ; an oval, oblong, two-celled, two-valved, 

 silique; smooth concave valve*, with an ensiform Madiera benk, 



scarcely shorter than the valves ; the seeds globose. The s|>ecies are 

 annual branched herbs, with erect terminal racemes of flowers, which 

 are white and yellow, and remarkable for their beautiful reticulation 

 of brown veins. 



E. m/ira, Garden-Rocket, has lyrate pinnatifid leaves, with toothed 

 acute lobes, a hairy stem, the pedicels shorter than the deciduous 

 calyx. It is a native of cultivated fields and waysides in the north 

 of Africa, in Spain, Portugal, France, Italy, Switzerland, and Greece, 

 It is very subject to varieties, and many have been described by 

 various botanists. Although mostly hairy, sometimes its stem is 

 smooth. In height it varies from three inches to two feet, and the 

 flowers are very variable in the depth and arrangement of their 

 colours. When full grown it has an acrid and unpleasant taste, and 

 a strong, peculiar, almost fetid smell ; but when young and tender 

 it is frequently eaten as a salad, especially on the Continent. It is 

 the Roquette Cultivee and La Rocket des Jardius of the French, 

 Raukette of the Germans, and Ruccola of the Italians. The whole 

 plant has been used hi medicine as a sialagogue. The ripened seeds 

 are a good substitute for the seeds of the mustard, but not so pungent. 

 When cultivated as a salad, the seeds should be sown in a warm 

 border early in February, and again in March and April for successive 

 crops. The plants should be thinned, after they have produced the 

 first rough leaves, to about three or four inches apart, and they 

 should be kept clear of weeds. If a supply is required throughout 

 the year, the seeds may be sown every month. The plants sown in 

 February should be allowed to produce seed, which ripen in August, 

 and may be used for all the sowings. E. hitpida and A', micaria are 

 European plants, and when cultivated ag ornament need only to be 

 sown in the open border and t rented as other hardy annuals. 



(Lindley, Flora Medica; Don, DiMamydtoiu Plantt.) 



ERUCASTRUM, a genus of Plants belonging to the natural order 

 Crucifcra, and to the tribe Sratticae. It has a square pod, the 

 valves convex, with one straight nerve, the seeds oval or oblong in a 

 single row. This genus has been formed by Schimper and Spenner 

 for some of the species of the old genus Sinajri*. }'. incanum, the 

 Sinapit intanut of Linnirux, has been found in sandy places in Jersey 

 and Alderney, and has consequently a place in the British Flora. It 

 has adpressed pods, which are turgid, with a short one-seeded beak. 

 The stem reaches from one to three feet high. This plant is also a 

 native of the South of Europe, especially Spain : and is the Caltile 

 Jfupanica of L'Heritier; the llirtcltfiddia adprctta of Moench. 

 Koch, in the ' Synopsis Flonc Germanicaj et Helvetica;,' gives three 

 species of this genus as natives of Switzerland and the upper dis- 

 trict of the Rhine. (Babington, Manual of Jiritith liotany ; Don, 

 JHi-lilamyilcoiu Planti.) 



ERUCIVORA. [LANUDX.] 



ERVUM, a genus of Plants belonging to the natural order 

 Li ijuminoiir aud the tribe Yicitec. It is known by a 6-cleft calyx, with 

 linear acute segments, about equal in length to the corolla ; glabrous 

 stigma; an oblong 2-4-seeded legume. Most of the species of this 

 genus are weeds, two of which, the E. hirttUum aud /.'. titrii.ijnni<um, 

 are found in Great Britain. The former is called Tine-Tare, and is a 

 great pest in corn-fields. 



E. Lent is the plant which produces the Lentil. It has branched 

 stems; oblong nearly glabrous leaflets, usually eight in 'number; the 

 stipules lanceolate and ciliated ; the peduncles 2-3-fiowered, about 

 equal in length to the leaves; the legumes short, broad, finely reticu- 

 lated ; seeds two, compressed. It is a native of corn-fields on the 

 continent of Europe. Lentils are not much eaten in this country, 

 but they are consumed in considerable quantities in France, Germany, 

 and Italy. The Lentil is one of the oldest leguminous plants u-.-.l .-i - 

 food of which we have any record. Ever since the time of Esau they 

 have been eaten in the East. In Egypt and Syria they are parched 

 in a frying-pan and sold in the shops, and are OOJHldmd by the 

 natives as the best food for those who are on long journey*. The 

 Lentil is still cultivated in this country. There are three varieties 

 known in France and Germany : the small brown, which is the lightest- 

 flavoured and the best for soups ; the yellowish, which is a little 

 larger and the next best; and the Lentil of Provence, which is almost 

 as large as a pea, with luxuriant straw, aud it might be cultivated 

 as food for cattle. 



In its cultivation the Lentil requires a dry warm soil ; it should bo 

 sown later than the pea, at the rate of a bushel or a bushel and a 

 half to the acre. It ripens earlier than the pea, aud requires the 

 same treatment and harvesting. The produce of the Lentil in grain 

 is about a fourth less than that of the tan, and the straw is not more 

 than a third as much. The straw is however considered very 

 nourishing, and is used for feeding calves and lambs. Lentils, like 

 all other leguminous fruits, contain a large quantity of uitrogenised 

 matters. Einhoff found that 3840 parts of lentils contained 1260 

 part* of starch and 1433 parts of a matter analogous to animal matter. 

 In a late analysis made by Dr. Playfair for the Royal Agricultural 

 Society be found that 100 parts of lentils contained 33 parts of 

 albumen or gluten and 48 parts of starch, Ac. ; whilst the same 

 quantity of peas contained 20 parts of albumen, and of beans 

 31 parts. If the theory of nutrition propounded by Professor 

 Ucbig in his late work on 'Animal/Chemistry' be correct, then lentils 

 constitute one of the most highly nutritious foods in nature. 



