T R A 



probably thrown up, and fpread over the furface in a fluid 

 llate. Wherever tliefe dykes pafs through the chalk, they 

 have converted it into cryftalline lime-ftone to a certain dif- 

 tance on each fide, and produced various appearances, which 

 tend further to prove that the matter of the bafalt has been 

 in a ftate of igneous fufion. See Veins, Mineral. 



That the bafalt has been forced through the chalk and the 

 other ftrata on which it now refts, is rendered almoft certain, 

 by the occurrence of broken ftrata of chalk enveloped in the 

 bafalt, and contorted in a manner which proves the violence 

 of the difrupture, the upheaving of the bafalt, and the lateral 

 preffure to which the chalk-ftrata have been fubjefted. See 

 Plate IV. Geology, Jig. 4. 



One remarkable feature in the arrangement of the bafaltic 

 columns in Antrim muft not be overlooked. The great 

 ranges of columns are nearly vertical, but the columns of 

 bafalt in the mineral dykes are arranged horizontally. This 

 difference of pofition may admit of a probable folution, if 

 \Ve allow that the bafalt, in both inftances, had been in a 

 ftate of igneous fufion. The beds of columnar bafalt being 

 thrown over the furface of the ground that formed the bed 

 of the ocean, would begin to refrigerate at the upper and 

 under fide in a vertical diredlion. On the contrary, in mi- 

 neral dykes interfefting rocks already formed, the bafalt 

 would fuffer refrigeration moft rapidly where it was in con- 

 tafl with them, which would be on the fides, and this refri- 

 geration would gradually extend to the interior, in a hori- 

 zontal direftion : and to this difference in the mode of their 

 confohdation, we may afcribc the horizontal or vertical po- 

 fition of the columns in the beds and dykes of bafalt. For 

 an account of the experiments of M. G. Watt and fir James 

 Hall on the fufion of bafalt and lava, fee Rowley Rag, 

 and Volcano. 



TRAi'-Hole, in Rural Economy, a term applied to a 

 round hole, which is cut out and prepared in the floors of 

 the ftowage-rooms, where hops are depofited after being 

 dried, for the purpofe and convenience of bagging them. 

 It is formed exaftly equal in fize to the mouth or opening 

 of the bag, around which a wooden frame is fecurely placed 

 and fixed, to the edge of which, the border of the mouth 

 of the bag is firmly attached all round. By this means the 

 hops are readily forced into the bags in a clofe compaft 

 manner. 



The term is alfo occafionally applied to other holes cut 

 and formed in the floors of farm-buildings. 



Trai'k, Garden, fuch as are contrived for the purpofe of 

 deftroying mice and other vermin ; which are often con- 

 veyed into fuch places with the ftraw, litter, and other 

 matters that are made ufe of in them ; and which are ex- 

 tremely hurtful and troublefome in the fpring feafon, in de- 

 ftroying peas and beans, as well as lettuces, melons, arrd 

 cucumbers in frames. 



Traps for this purpofe are- contrived in a great many 

 ways ; but as field vermin are very fhy, and will rarely enter 

 ti-aps which are clofe, the following fimple cheap form has 

 been advifed by Mr. Forfyth, though it has nothing of 

 novelty in it. Thefe traps may be made by ftringing garden- 

 beans on a piece of fine pack-thread, in the manner of beads, 

 and then driving two fmall ftake-like pieces of wood into 

 the ground at the breadth of a brick from each other, and 

 fetting up a brick, flat ftone, or board with a weight on it, 

 inclining to an angle of about forty-five degi-ees ; tj-ing the 

 firing, with the beans on it, round the brick or other fub- 

 ftances and ftakes, to fupport them in their inclining pofi- 

 tion, being careful to place all the beans on the under fides 

 of the bricks or other matters. The mice in eating the 

 beans, in fuch cafes, will alfo deftroy the pack-thread, and 



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by fuch means difengage the brick or other weighty body, 

 which by falling on them readily deftroys them. 



Mice are always the beft got rid of by fome fort of 

 fimple open traps of this nature. 



TRAPA, in Botany, a Linnsean name, whofe idea is 

 certainly taken from the warlike inftrument called Caltrop, 

 the Tribulus of the ancients, which confifted of four iron 

 radiating Ipikes, fo placed that one of them mull always 

 ftand upwards, ni order to wound the feet of paflengers. 

 Such is the figure of the lingular fruit of tbjs genus, hence 

 named by Tournefort Trlbuluides. Calcitrapa, an old bo- 

 tanical word of fimilar meaning to Tribulus, is compounded 

 perhaps of calco, to tread, or hick, and ~i'--j, to turn, becaufe 

 the Caltrops are continually kicked over if they fail of their 

 intended mifchief. Here we have the immediate origin of 

 Tra/a.— Linn. Gen. 62. Schreb. 84. Willd. Sp. PI. 

 v. I. 681. Mart. Mill. Dift. v. 4. Ait. Hort. Kew. v. i. 

 267. Sm. Prodr. Fl. Grsec. Sibth. v. i. 104. Jufl". 68. 

 Lamarck Illuftr. t. 75. Grsrtn. t. 26. and t. 95. (Tribu- 

 loides ; Tourn. t. 431.) — Clafs and order, Teirandria Mono- 

 gynia. Nat. Ord. Inundala, Linn.? Hydrocharides, Juff. 

 or rather, as that author himfelf indicates, his Onagrx. 



Gen. Ch. Cal. Perianth fuperior, of four acute, equal, 

 permanent leaves, firmly united to the fides of the germen. 

 Cor. Petals four, obovate, larger than the calyx. Stam. 

 Filaments four, the length of the calyx ; anthers fimple. 

 Pijl. Germen turbinate, crowned by the calyx, of two cells ; 

 ftyle fimple, as long as the calyx ; ftigma capitate, emar- 

 ginate. Peru. none. Seed. Nut turbinate, more or lefs 

 comprefled, of one cell, armed %vith two or four horn-like 

 protuberances, originating ia the permanent calyx, tliickened, 

 either fpinous or blunt. Kernel folitan'. 



Eff. Ch. Corolla of four petals. Calyx of four leaves. 

 Nut armed with two or four oppofite horns, originating iu 

 the leaves of the calyx. 



I. T. natans. European Water-caltrops. Linn. Sp. 

 PI. 175. Suppl. 128. Willd. n. I. Ait. n. i. Prodr. 

 Fl. Grsec. n. i. Gasrtn. t. 26. (T. aquaticus ; Camer. 

 Epit. 715. Matth. Valgr. v. 2. 324. Ger. Em. 824.) — 



Nuts with four fpinous afcending horns Native of ponds 



and muddy ditches in the fouth of Europe, flowering in fum- 

 mer. The plant is annual, and has feveral times been brought 

 into England ; but whether its feeds are not perfected here, 

 or from any other caufe, it has never yet been naturalized. 

 The ponds at VerfaiUes abound with this Trapa. The foli- 

 tary fibrous root fends up a long, cylindrical, floating_y?fm, 

 varjnng in length according to the depth of the water, fur- 

 nifhed with numerous, oppofite, peftinated tufts of fibrous 

 radicles, gradually diminifhing to fimple fibres, and at the 

 top of the ftem, which is thickened, thefe fibres are replaced 

 by alternate ftalked leaves, which are crowded at the fummit 

 into a large fpreading ftar, floating on the furface of the 

 pool, and often ten or twelve inches in diameter. Each leaj" 

 is rhomboid, fucculent, an inch or more in breadth, veiny ; 

 ftrongly toothed in front ; eotire at the bafe ; the veins rather 

 hair)' underneath. Footjlalks three or four times as long as 

 the leaves, fmooth, fweUing beyond the middle into an eUip- 

 tical cellular body, rendering the plant more buoyant. 

 Flonvers fmall, white, on fhort, club-fliaped, axillary, fimple, 

 partly hairy ftalks, fcarcely half an inch long. Nuts turbinate, 

 about an inch in diameter, angular, fmooth, with four, by 

 accident only two or tliree, prominent afcending pointed 

 horns, becoming lateral by the increafe of the fummit of the 

 germen, two of them fituated at the angles of the nut, two 

 lower down at the fides. The kernel is eatable, fomewhat 

 like a chefnut. This plant is doubtlefs the r^i;9o>o,- eivJjo; of 

 Diofcorides, found by Dr. Sib thorp in countries bordering 



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