7l6 PHILOSOPHICAL TRANSACTIONS. [ANNO 1800. 



when immersed 14 days or more in the dilute acid, were very little affected, ex- 

 cepting that they became softer and transparent, so as to approach the characters 

 of cartilage or softened horn*. The acid in which they had separately been 

 steeped, did not afford any precipitate by the addition of the alkalies ; and the 

 only change was in the colour, which became deep yellow when ammonia was added. 



The gorgoniae now to be mentioned differ from the former, as they are not 

 coated with a fleshy or pulpy cortical substance. They are here placed immediately 

 before the antipathes, on account of their great similarity in chemical properties, 

 as well as in external appearance. 



Gorgonia antipathes. — Some pieces of this gorgonia were immersed in dilute 

 nitric acid 3 weeks, at the end of which time they were much softened, and ap- 

 peared to be composed of a pale brown opaque membranaceous substance, which 

 formed concentrical coats, of a ligneous aspect. The acid in which these pieces 

 had been steeped, was become pale yellow, and changed to orange colour when 

 ammonia was added ; but not the smallest precipitate could be thus obtained ; nor 

 was any alteration caused by the addition of lixivium of potash. When distilled 

 water was boiled with the gorgonia antipathes about 6 hours, it became slightly 

 tinged with yellow ; and some infusion of oak bark being added, a small quantity 

 of gelatin was precipitated. The pieces of this substance which had been thus 

 treated, were afterwards boiled with lixivium of caustic potash, by which the 

 whole was dissolved, and a very dark coloured animal soap was formed. When 

 this gorgonia was exposed to a red heat, it emitted much smoke, with a smell of 

 burnt horn : it soon lost its shape, puffed up, and formed a spongy coal, which, 

 by a long continued heat, left a few particles of a white substance, consisting 

 chiefly of muriate of soda. 



Another species of gorgonia was next examined, the stem of which is from -^ 

 to nearly 4- an inch in diameter in the thickest parts; it is of a black colour, and 

 a high polish, like black sealing wax : it has probably been considered as a variety 

 of gorgonia antipathes. This by immersion for 28 days in dilute nitric acid, gra- 

 dually became semi-transparent, and of a bright brownish yellow. In this softened 

 state, it was steeped 2 days in water, and was then opened longitudinally. By this 

 the whole structure became apparent, and consisted of thin coats or tubes of a 

 beautiful transparent membrane, which, beginning from a central point, progres- 

 sively became larger, according to the order by which they receded from the centre. 

 These membranes were so delicate, that the fibrous texture could scarcely be dis- 

 cerned. The acid in which this species had been steeped was tinged with very pale 

 yellow. Ammonia being added, changed it to a deep yellow or orange colour ; 

 but the transparency of the liquor was not disturbed by this, or any of the other 

 precipitants which had been employed in the former experiments. When this 



* The stems of the various gorgoniae, which had been thus softened by long immersion in dilute 

 nitric acid, became of a deep reddish orange colour, inclining to brown, when subsequently steeped 

 in pure ammonia } and in the course of a few hours they were completely dissolved.— Orig. 



