On the Arragonite of Werner.-^andafac. , 569 



The vertical feftion of the prifms of the arragonite prefent another fingularity noticed 

 by Born ; it is a kind of crofs, compofcd of four triangles, amongft which thofe whofe 

 bafes are horizontal, are of a pale colour ; and the other two, whofe bafes are vertical, 

 are of a more intenfe violet colour. 



Fig. 2. reprefents a prifm of arragonite, where the four cuneiform o£tahedrons which 

 compofe it, are very diftinft- 



VII. 



On the true Origin of Re/in, known by the Name £/"Sandarac, and on that of Gum Arabic, 



by M. ScHovSMOE *. 



OaNDARAC is an article of commerce, which is brought from the weftern provinces , 

 of the kingdom of Morocco. From fix to feven hundred quintals are annually {hipped in 

 the ports of Santa Cruz, Mogador, and Saffy. This refin is called, in the language of 

 the country el grajfa. The tree which produces it is a thuia, which was alfo found in the 

 kingdom of Tunis by M. Vahl, who has given a complete defcription, and a good figure 

 of it in his work, entitled, Symbol. Botan. part the and, page 96. PI. XLVIII. by the 

 name of Thuia Articulata. Shaw had formerly made it known, and called it Cyprejfus, 

 fruEiu quadrivahi, foliis equifeti inflar artkulatls ; but neither of thefe learned men were 

 acquainted with the ceconomical ufe of this tree, probably becaufe as it is feldom met 

 with in the northern parts of Barbary, too little advantage can be derived from the refin 

 which flows from it. 



Till the prefent time this refin was attributed either to the Juniperus Communis, or to 

 the Juniperus Lycia, or laftly to the cedar of Libanus, without confidering that the 

 Juniperus Communis is not found in Africa ; and that the Sandarac appears to come 

 exclufively from that part of the world. M. Schoulboe, who has feen the fpecies of thuia 

 here alluded to, fays, that its height never exceeds 8 metres [i6\ feet), and that the 

 diameter of Its trunk is not more than 20 or 22 (7 inches) centimetres. It is diftinguifhed 

 at firft fight, from the two other fpecies of the fame kind of tree, which are cultivated 

 in our gardens, by having a diflinft trunk, and the appearance of a real tree, whilft in the 

 others the branches iflue out from the root, which gives them rather the refemblance of 

 bulhes. Its branches alfo are more articulate and more brittle ; its bloflbms, which arc 

 not very apparent, difplay themfelves in germinal, (April), and its fruits, the form of which 

 is nearly fpherical, ripen in Fruftidor, (September). 



By prefenting a branch of this vegetable to the light, it is obferved to be covered with 

 a multitude of tranfparent veficles, which contain the refin. After thefe veficles have 



• Extrafted by Ch. Coquebert, from the Danifli Journal, entitled, Bibliot. de Phyfi<^ue, medicine et 

 economie, 3d cahier, 1799, and inferted in the Bulletin de U Soc. Philom. No. 31. 



Vol. IV. — November 1800, 3 B burft 



