S T R 



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S T R 



but reserved for general reasoning. Mr. 

 Bakewell observes, " though the word 

 stratum, in its original language, and by 

 general acceptation in speaking of rocks, 

 denotes a bed, it is convenient to restrict 

 the term bed to a stratum of considerable 

 thickness ; for such beds are often sub- 

 divided into several distinct minor strata, 

 and we cannot well describe a stratified 

 stratum." The true thickness of a stra- 

 tum is measured by a line perpendicular 

 to the upper and under surface, let its 

 inclination be whatever it may. 



STREAK, (strich, Germ.) In mineralogy, 

 the appearance of a mineral which arises 

 from its being scratched by a hard sharp 

 instrument. The streak is said to be 

 similar, when the colour of the powder 

 produced by scratching the mineral is the 

 same with the colour of the mineral itself ; 

 when the colour varies, the streak is said 

 to be dissimilar. 



STREPSI'PTEBA. An order of insects, pa- 

 rasitic animals, that have two ample 

 wings, forming the quadrant of a circle, 

 and of a substance between coriaceous 

 and membranous ; and two elytriform 

 sub-spiral organs, appendages of the base 

 of the anterior legs. The above is Mr. 

 Kirby's description of the order he has 

 named Strepsiptera ; Latreille has given 

 to this order the name Rhipiptera. 



STRIDE, (stria, a streak, Lat. stries, Fr. 

 This word is used in the plural only. ) 



1. In conchology, striae are fine thread- 

 like lines, generally on the exterior sur- 

 face of shells, longitudinal, transverse, or 

 oblique. 



2. In botany, fine thread-like lines run- 

 ning in parallel directions. 



STRI'ATED. (strie, Fr.) Arranged in fine 

 lines running parallel to each other, let 

 the direction of the lines be what it may. 

 Marked with fine thread-like lines run- 

 ning parallel to each other. 



STRIKE, (stretch, Germ, stroke, stripe.) 

 The line of bearing of strata. The strike 

 or direction of strata is always at right 

 angles to their dip. 



STRO'BIL. } (from stroMlus, Lat.) In bo- 



STRO'BILE. $ tany, a pericarp formed from 

 an ament by the hardening of the scales ; 

 a catkin hardened and enlarged into a 

 seed-vessel; a seed-vessel composed of 

 ligneous scales. 



STRO'MBITE. A fossil strombus ; a petri- 

 fied strombus. Strombites are very rare : 

 Lamarck describes one shell only of the 

 genus strombus, as found in the environs 

 of Paris. In the mountains of Arragon, 

 and in the Veronese, some specimens 

 beautifully preserved have been disco- 

 vered. 



STRO'MBUS. The name given by Linnaeus 

 to a genus of univalve, spiral, marine, 



shells ; aperture jnuch dilated : lip ex- 

 panding and produced into a groove. 

 Lamarck has divided this genus into two 

 subgenera, Strombus and Pteroceras. In 

 some of the shells of this genus the spines 

 are of great length, and are arranged 

 round the circumference of the base, 

 being at first tubular, and afterwards solid, 

 according to the period of growth. In 

 Turton'sLinne fifty-five species of strombi 

 are described ; of these, two only have 

 been found in the seas of this country. 

 STRO'NTIA. } A mineral was brought to 

 STRO'NTIAN. \ Edinburgh about the year 

 1787, from the lead-mine of Strontian in 

 Argyleshire, from which was obtained the 

 earth thus named by Klaproth. It has 

 subsequently been found in England, 

 America, and France. It is sometimes 

 transparent and colourless, but generally 

 has a tinge of yellow or green. Its hard- 

 ness is 5. Specific gravity from 3*4 to 

 3*9. Its texture is generally fibrous ; 

 sometimes it occurs crystallized in slender 

 prismatic columns of various lengths. 

 The mineral is composed of carbonic acid 

 and a peculiar earth, to which Dr. Hope 

 gave the name of Strontites, and Klaproth 

 that of Strontian. The carbonic acid 

 may be expelled from the carbonate, and 

 the strontian obtained pure, by mixing 

 the mineral with powdered charcoal, and 

 exposing it to a heat of 140 Wedgewood. 

 When strontian is combined with sul- 

 phuric acid, forming a sulphate of stron- 

 tian, it may be separated from the sul- 

 phuric acid by mixing the mineral with 

 the eighth part of its weight of charcoal- 

 powder, and keeping it for some hours 

 red-hot in a crucible ; it will then be 

 reduced to a sulphuret of strontian. Dis- 

 solve the sulphuret in water, and pour 

 nitric acid into the solution, the sulphur 

 will then be precipitated. This solution, 

 which consists of nitric acid combined 

 with strontian, is to be filtered and eva- 

 porated slowly till it crystallizes. The 

 crystals are then to be put into a crucible, 

 and subjected to a strong heat, the nitric 

 acid will be driven off and pure strontian 

 remains. 



Strontian is of a greyish-white colour ; 

 its taste is acrid and alkaline ; it converts 

 vegetable blues to green. The principal 

 use of strontian is to communicate a 

 beautiful red colour. 



STRO'NTIANITE. Carbonate of strontian. 

 The Strontian carbonatee of Haiiy ; 

 Strontianit of Werner ; Strontiane of 

 Jameson ; Stronthianite of Kirwan. A 

 mineral first brought to Edinburgh from 

 the lead-mines of Strontian, in Argyle- 

 shire, in the year 1787. It greatly re- 

 sembles carbonate of barytes, but it is not 

 poisonous. 



