A G G 



i a 



and, from its hardness and compact 

 structure, being capable of receiving 

 a high polish, occupies a distin- 

 guished position in most collec- 

 tions." Professor Jameson places 

 Agate amongst the members of the 

 Quartz family, constituting it a 

 distinct species. He says "it is 

 not, as some mineralogists main- 

 tain, a simple mineral, but is com- 

 posed of various species of the 

 quartz family, intimately joined 

 together. It is principally com- 

 posed of calcedony, with flint, horn- 

 stone, carnelian, jasper, cacholong, 

 amethyst, and quartz." Professor 

 Cleaveland says " the calcedony is, 

 however, the most common and 

 abundant ingredient, and may fre- 

 quently be considere'd the base of 

 the agate ; in fact, some agates are 

 composed entirely of calcedony dif- 

 ferently coloured." Werner divided 

 agates into Ribbon Agate ; Fortifi- 

 cation Agate; Breeciated Agate; 

 Moss Agate; Landscape Agate; 

 Tubular Agate ; and Jasper Agate. 

 As precious stones, agates are now 

 less esteemed than formerly: the 

 most valuable are the oriental. 

 When cut and polished, agates pre- 

 sent an appearance of waving lines, 

 sometimes accurately parallel, some- 

 times varying in breadth, and some- 

 times containing a resemblance to 

 vegetable forms, as mosses, ferns, 

 &c. Small agates are frequently 

 found in common gravel. 



A'GATY. Of the nature of agate. 



A'GGSEGATE. (aggregat, Fr.) 



1. The complex, or collective re- 

 result of the conjunction, or acer- 

 vation, of many particulars: it 

 differs from a compound body, in- 

 asmuch as the union in the last is 

 more intimate than between the 

 parts of an aggregate. 



2. In botany, a term used to ex- 

 press flowers composed of many 

 small florets, having a common 

 undivided receptacle; tho anthers 

 separate and distant, the florets 



commonly standing on stalks, each 

 having a single or double partial 

 calyx. They are opposed to simple 

 flowers, and are usually divided 

 into seven kinds. 



AGGREGATED. Collected ; accumu- 

 lated ; heaped together. A rock is 

 said to be aggregated when the 

 several parts of which it is com- 

 posed merely adhere and may be 

 separated from each other by me- 

 chanical means : thus in granite, 

 the several parts of which, quartz, 

 mica, and felspar, may be mechani- 

 cally separated, we have an instance 

 of an aggregated rock. 



AGGBEGA'TIOW. (aggregation, Fr. ag- 

 gregazione, It.) The collection into 

 one mass of bodies having no natu- 

 ral connexion, but, by a species of 

 union, made to constitute one body. 



AGSTO'STUS. (a^vica-ro^, Gr.) A fossil 

 genus of trilobites, established by 

 Brongniart, the Battus of Dalman. 

 Agnosti are found in the lower 

 Silurian rocks, especially in the 

 Llandeilo flags. In Norway, says 

 Sir E. Murchison, the Agnosti 

 occur in millions, but in our 

 rocks they are much less fre- 

 quent. Macleay does not consider 

 Agnostus to belong to the Trilo- 

 bita. The discovery of an entire one 

 in Bohemia, by Dr. Beyrich, proves 

 the agnostus to be a true trilobite. 



AGNOTHE'RIUM. An extinct animal 

 of the miocene period, order Mam- 

 malia, allied to the dog, but of very 

 large size. One species only has 

 been found, at Epplesheim, in 

 Germany. 



AIGUE MAHI'KE. A variety of topaz, 

 of a blueish or pale green colour. 



AIGUI'LLES. (aiguilles, Fr.) The 

 needle-like points, or tops, of 

 granitic rocks. 



AIGUI'LLB DE DKTT. A pyramidal 

 granitic mountain, according to 

 Bakewell, the most remarkable at 

 present known; the upper part, 

 or spire, rises above its base nearly 

 to a point, in one solid shaft, moro 



