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A G G 



through the air, we must conclude that 

 they are exceedingly numerous ; more 

 especially, when we reflect on the small 

 proportion which must be observed, and 

 the small comparative portion of the 

 globe which is inhabited, or habitable, by 

 man. 



AERO'METER. (from arjp and n'trpov, Gr. 

 acrometre, Fr.) An instrument for ascer- 

 taining the weight, or density, of the 

 atmosphere. 



AERO'METRY. (ae'rometrie, Fr.) The 

 science which treats of the properties of 

 the air ; it comprehends not only the 

 doctrine of the air itself, considered as a 

 body, but also its pressure, elasticity, 

 rarefaction, and condensation. 



AERO'SCOPY. (from drjp and (TKOTrsw, Gr.) 

 The observation of the air. 



^RU'GINOUS. (from ceruginosus, Lat.) 

 Partaking of the nature of the rust of 

 copper. 



,/ERU'GO. Verdigrease, or verdigris ; rust 

 of copper, formed by the combination of 

 an acid with copper. Impure subacetate 

 of copper. Verdigris is inodorous, and 

 when first applied to the tongue is nearly 

 insipid, though strongly styptic ; it leaves 

 a metallic taste in the mouth. It is poi- 

 sonous ; sugar acts as a specific against 

 its poisonous effects. 



^E'STIVAL. ((Bstivalis, Lat.) Pertaining to 

 summer. 



JE'STIVAL PLANTS. Plants which flower 

 during the summer. 



^ESTIVA'TION. (cestivatio, Lat.) 



1. The eifect produced by summer heat. 



2. The mode in which the parts of a 

 flower, taken separately, are arranged in 

 the bud. 



jE'xiTES. (atroc, Gr. aetite, Fr.) Eagle- 

 stone ; a variety of oxide of iron mixed 

 with clay. It is found in masses, gene- 

 rally under the form of a rounded knob, 

 something resembling a kidney. It pre- 

 vails in the coal formations of England, 

 Wales, and Scotland, has a rough surface, 

 and is of a brown colour. Specific gra- 

 vity 4 to 7. Lustre of the exterior 

 metallic. It frequently contains a sort of 

 kernel, which rattles on being shaken. 

 It was formerly in repute for several 

 extraordinary magical as well as medical 

 properties, such as preventing abortion, 

 discovering thieves, &c. It derives its 

 name from a popular notion that it was 

 found in eagles' nests, where it was sup- 

 posed to prevent the eggs from becoming 

 rotten. See Nodular Iron Ore. 



^ETI'TES LAPIS. Eagle-stone. See JEti- 

 tes. 



AFFI'NITY. (affinite, Fr. affinita, It.) The 

 tendency which bodies, dissimilar in their 

 composition, have to unite and form new 

 compounds. Different bodies are pos- 



sessed of different attractive powers, and 

 if several be brought together, those 

 which have the strongest mutual affini- 

 ties enter first into union. Affinity, like 

 sensible attraction, varies with the mass 

 and the distance of the attracting bodies. 

 That the force of affinity increases as the 

 distance diminishes, and the contrary, is 

 obvious ; for it becomes insensible when 

 the distance is sensible, and exceedingly 

 great when the distance is exceedingly 

 diminished. Affinity agrees with sensible 

 attraction in every point which it has been 

 possible to determine. 



AGALMA'TOLITE. (from d-ya\p,a and Xi0oc, 

 Gr.) Figure-stone. A sub-species of 

 talc-mica, of different colours, as white, 

 red, brown, green, and grey. It occurs 

 massive. It feels greasy, is translucent, 

 and has a conchoidal fracture. The 

 finest specimens are brought from China. 

 It does not contain any magnesia, but in 

 other respects it has the characters of 

 talc. 



A'GARIC. (agaricus, Lat.) The generic 

 name for the mushroom, a genus of the 

 order Fungi, class Cryptogamia. Gmelin 

 enumerates nearly 400 species. 



A'GARIC MINERAL. A variety of soft car- 

 bonate of lime. It is found in the clifts 

 of rocks, or the bottom of lakes, in pieces 

 loosely cohering, and it is so light as 

 nearly to swim upon water. It obtains 

 its name from its resemblance to a fungus 

 in colour and texture. 



A'GATE. (achates, Lat. d%arrjc, Gr. agate, 

 Fr. agata, It.) A siliceous, semi-pellucid 

 gem, of which there are many varieties, 

 not of great value. Agates are princi- 

 pally composed of quartz with various 

 colouring matters. Agates may be arti- 

 ficially coloured by immersion in metallic 

 solutions. Amongst the varieties of 

 agate may be enumerated, calcedony, car- 

 nelian, onyx, sardonyx and heliotrope. 

 As precious stones, agates are now less 

 esteemed than formerly ; the most valua- 

 ble are the oriental. When cut and 

 polished, agates present an appearance of 

 waving lines, sometimes accurately paral- 

 lel, sometimes varying in breadth, and 

 sometimes containing a resemblance to 

 vegetable forms, as mosses, ferns, &c. 

 Small agates are frequently found in com- 

 mon gravel. 



A'GATY. Of the nature of agate. 



AGGELA'TION. Concretion by freezing. 



A'GGEROSE. (from agger, Lat.) Full of 

 heaps. 



AGGLU'TINANT. (agglutinant, Fr.) That 

 which has the power of uniting parts 

 together. 



AGGLU'TINATE. (agglutino, Lat.) To 

 cause to adhere ; to glue together. 



AGGLUTINA'TION. (agglutination, Fr.) 



