APS 



A R A 



This substance is called also Ich- 

 thyoplithalmite, and Fish-eye stone. 

 It occurs both massive and regular- 

 ly crystallized. It is found in 

 Sweden, in secondary traprocks in 

 Scotland and the Hebrides, and in 

 Iceland, whence the finest speci- 

 mens are obtained. 



APO'PHYSIS. (airofaffis, Gr. apophyse, 

 Fr.) A process of a bone, and 

 part of the same bone; herein 

 differing from ephiphysis, which is 

 a process attached to a bone, and 

 not a part of the same bone, an 

 excrescence. 



APORRHA'IS. A genus of shells found 

 fossil and recent. The Aporrhais 

 first appears fossil in the coralline 

 crag epoch. 



APPE'NDAGE. Something added to 

 another thing, without being ne- 

 cessary to its essence. In botany, 

 applied to additional organs of 

 plants, which are not universal or 

 essential ; neither is any one plant 

 furnished with them all. Botanists 

 distinguish seven kinds of ap- 

 pendages, namely, stipules, floral 

 leaves, thorns, prickles, tendrils, 

 glands, and hairs. 



APPENDI'CULATE. Appendicled, or 

 appended. Applied to flowers fur- 

 nished with some addition distinct 

 from the tube ; to petioles with 

 leafy films at the base; to seeds 

 furnished with hooks, scales, &c. 



APPRE'SSED. (appressus, Lat.) In 

 botany, applied to leaves pressed 

 to the Btem ; also to peduncles. 



A'PSIDES. (apsides, Fr. from atyls, 

 Gr. The plural of apsis,) Those 

 two points in the orbit of a planet, 

 one of which is the farthest from, 

 and the other the nearest to, the 

 sun. The motion of the apsides 

 may be represented, by supposing 

 the planet to move in an ellipse, 

 while the ellipse itself is slowly 

 revolving about the sun in the 

 same plane. This motion of the 

 major axis, which is direct in all 

 the orbits except that of the planet 



Venus, is irregular, and so slow, 

 that it requires more than 109,830 

 years for the major axis of the 

 earth's orbit to accomplish a side- 

 real revolution. 



A'PSIS. (ai/r/s, Gr. apsis, Lat.) A 

 term used indifferently for either 

 of the two points of a planet's 

 orbit, where it is at the greatest or 

 least distance from the sun or 

 earth ; and hence the line connect- 

 ing those points is called the line 

 of the apsides. The apsis at the 

 greatest distance from the sun is 

 called the aphelion, and at the 

 greatest distance from the earth is 

 called the apogee-, while that at 

 the least distance from the sun is 

 termed the perihelion, and at the 

 least distance from the earth, the 

 perigee. 



A'PTER. | (from a, priv. and n-repbv, 



A'PTERA. j a wing.) Insects which 

 have no wings, forming, according 

 to the LinnaBan system, the seventh 

 order of insects. 



A'PTEROUS. Destitute of wings, wing- 

 less. 



APTIEN TERRAIN. The continental 

 name for certain beds contempo- 

 raneous with the Lower Greensand 

 of England. 



A'PULUM. The name of a metallic 

 substance obtained from alumina. 



API'ROTJS. (from a, priv. and iri>p t Gr. 

 apyre, Fr.) Capable of resisting 

 the action of fire. 



ARA'CHNIDA. | (from apd^vij and 



ARA'CHNIDAN. ) e?ov, Gr. resem- 

 bling a spider.) The arachnida are 

 members of that series of annulose 

 animals possessing jointed feet, and 

 belong to the third class of articu- 

 lated animals. In the animal 

 kingdom, the third class of annu- 

 losa, comprising the following 

 orders, namely, Pulmonata, Am- 

 phipneusta, Trachearia, and Pycno- 

 gonida/ The two great families in 

 the higher order of living arachni- 

 dans are spiders and scorpions. 

 JBuckland. In the arrangement of 



