ELM. 



science to the cultivation of the earth has 

 hitherto not been very practically useful. Its 

 operations the very nature of electricity are 

 as yet much too little understood for the culti- 

 vator to derive instruction from its study. 

 "Electrical changes," said Davy (Elements of 

 Jlgr. Chem. p. 41), "are constantly taking place 

 in .nature on the surface of the earth, and in the 

 atmosphere: but as yet the effects of this 

 power in vegetation have not been correctly 

 estimated. It has been shown, by experiments 

 made by means of the voltaic battery (the in- 

 strument in which electricity is evolved by the 

 mutual action of zinc, copper, and water), that 

 compound bodies in general are capable of 

 being decomposed by electrical powers ; and it 

 is probable, that the various electrical pheno- 

 mena occurring in our system must influence 

 both the germination of seeds and the growth 

 of plants. I found that corn sprouted much 

 more rapidly in water positively electrified by 

 the voltaic instrument, than in water nega- 

 tively electrified ; and experiments made upon 

 the atmosphere show that clouds are usually 

 negative ; and as when a cloud is in one state 

 of electricity, the surface of the earth beneath 

 is brought into the opposite state, it is probable 

 that, in common cases, the surface of the earth 

 is positive. Different opinions are entertained 

 amongst scientific men respecting the nature 

 of electricity : by some, the phenomena are 

 conceived to depend upon a single subtile fluid, 

 in excess in the bodies said to be positively 

 electrified, in deficiency in the bodies said to 

 he negatively electrified ; a second class sup- 

 pose the effects to be produced by two different 

 fluids, called by them vitreous and resinous; and 

 a third set regard them as affections, or mo- 

 tions of matter, and merely an exhibition of 

 attractive powers, similar to those which pro- 

 duce chemical combination and decomposition, 

 but usually exerting their action on masses." 



ELEVATION, ATMOSPHERIC. The 

 height of land above the sea or common level, 

 exerts a very great influence upon the growth 

 of plants. One of the main causes operating un- 

 der such circumstances to diminish the size of 

 plants, Professor Dobereiner believes to be the 

 diminution of atmospheric pressure.' Experi- 

 ments have been made in order to prove this 

 by placing seeds of barley in vessels, contain- 

 ing soil, water, and air, under different degrees 

 of atmospheric pressure ; and the result has 

 been, that, where the pressure was greatest, 

 the vigour of the plants was also greatest. See 

 ALTITUDE. 



ELM (Ulmus). A genus of forest trees, 

 common in Great Britain, of which there are 

 several varieties. The characters of the genus 

 are flowers, bisexual ; calyx, bell-shaped, four 

 to five toothed, coloured persistent ; stamens, 

 three to six ; stigmas, two , fruit, sub-globular, 

 with a broad membranous margin. Sir James 

 E. Smith (Eng. Flor. vol. ii. p. 19), describes 

 five species of native elm: viz. 1. The com- 

 mon small-leaved elm (U. campestris}, which is 

 found chiefly in the southern parts of England. 

 The wood is hard and tough, particularly dura- 

 ble in wet situations, and is greatly preferred 

 in Norfolk (where it is the rm>st common spe- 

 cies) to any other, and sells for nearly double 

 440 



ELM. 



the price, serving more especially for the 

 naves of wheels. In other parts of England, 

 and particularly about London, the wood of the 

 common elm is used for coflins. 2. The com- 

 mon cork-barked elm (U. suberosa), which is 

 taller and more spreading than the foregoing. 

 The bark when a year old is covered with very 

 fine dense cork in deep fissures ; whence the 

 name. It is far inferior to the former in value. 

 There are various cultivated varieties raised 

 from seed. 3. The Dutch cork-barked elm (U. 

 mayor); a doubtful native. The branches 

 spread widely in a drooping manner, and the 

 bark is rugged, much more corky than even 

 the foregoing. Miller says this elm was 

 brought from Holland in King William's reign, 

 and being recommended for its quick growth, 

 was a fashionable tree for hedges in gardens, 

 but afterwards fell into disuse. He adds, that 

 " the wood is good for nothing, so its use is 

 almost banished in this country." 4. The 

 broad-leaved Scotch elm, or wych hazel (U. mon- 

 tana}. It is sometimes called the Hertfordshire 

 elm, being very frequent and luxuriant in that 

 county. The large hop-like fruit is abundant, 

 and very conspicuous in Mayor June; and 

 the seeds appear to be usually perfected. This 

 is one of the most general species of elm 

 throughout Europe. It is a large spreading 

 tree, of quicker growth than the common 

 small-leaved elm, and the wood is consequently 

 far inferior in hardness and compactness, and 

 more liable to split. The branches are in 

 some individuals quite pendulous, like the 

 weeping willow. The bark is smooth, and 

 downy in a young state. 5. The smooth-leaved, 

 or u-ych elm (U. glabra}. A tall, elegant tree, 

 with spreading, rather drooping, smooth, black- 

 ish branches, and smaller leaves than any of 

 the preceding, except the first. 



The elm (says Brande) is valued for the ra- 

 pidity of its growth, its hardness, and its capa- 

 bility of thriving in poor soil unfit for tillage. 

 Tredgold (Princip. of Carp.}, however, says the 

 elm is of slow growth. The elms of England 

 are scarcely less remarked for their age, bulk, 

 and beauty than the British oaks. The colour 

 of the heart-wood of elm is generally darker 

 than that of oak, and of a redder brown. The 

 sap wood is of a yellowish or brownish white, 

 with pores inclined to red. It has a peculiar 

 odour, is in general porous and cross-grained 

 sometimes coarse-grained, and has no large 

 septa. It twists and warps much in drying, 

 and also shrinks considerably both in length 

 and breadth. It is difficult to work, but not 

 liable to split, and bears the driving of bolts 

 and nails better than any other timber. What 

 is known in Europe as the twisted elm (Orme 

 tortillard), is not a distinct species but only a 

 variety of the European elm. The twisted 

 form of the fibres is secured by culture, the 

 young stalks being properly grafted and plant- 

 ed separately from the parent tree. In Scot- 

 land, chairs and other articles of household 

 furniture are frequently made of elm wood; 

 but in England, where the wood is inferior, 

 besides the purposes already specified, it is 

 chiefly in demand for the manufacture of casks, 

 mill-wheels, pumps, water-pipes, axletrees, &c. 

 It is appropriated to these purposes because of 



