AGALMATOLITE 81 



presence of certain reducing agents. Other experiments have been made by heating 

 iron, silicon, and magnesium, in an imperfectly oxidising atmosphere. 



It is perhaps unnecessary in this place to do more than refer to Dr. Mayer's 

 theory, which seeks to explain the source of solar heat by the impact of meteorites 

 falling into the mass of the sun a subject on which Mr. Waterston and Sir W. 

 Thomson have also written. It has even been suggested that the zodiacal light may 

 be a luminous crowd of meteoric stones showered down upon the sun. This hypo- 

 thesis has not, however, received the support it claimed, and the whole question 

 remains in a state of considerable uncertainty. 



AEROSTATION" ; AERONAUTICS. The ascent into the atmosphere by 

 means of balloons, which are either filled with hot air FIRE-BALLOONS, or a light 

 gas AIR-BALLOONS. 



The Montgolfier balloon is a bag filled with air, which is rarefied by the action of 

 fire, which is kept burning under the mouth of the bag ; and thus the whole mass is 

 rendered specifically lighter than the surrounding medium. 



The investigations of Cavendish led to the use of hydrogen gas the lightest of 

 known bodies to inflate silken bags ; and since his time our balloons have been inflated 

 with either pure hydrogen, or with common coal gas carburetted hydrogen. 



Notwithstanding the numerous attempts which have been made to navigate the air, 

 nothing has yet been done to enable the aeronaut to steer his balloon. In whatever 

 current of air he may be, with that current ho moves ; and, until this difficulty is 

 overcome, we cannot expect any satisfactory results from aeronautics. The great use 

 of balloons during the siege of Paris led to considerable improvements in the art of 

 aerostation. They were largely employed during the siege of Paris in enabling the 

 besieged to communicate outside the city. A balloon-post (Poste aerienne) was thus 

 established, and no fewer .than 54 ascents were made between October 1870 and 

 January 1871. M. Dupuy de Lome has constructed balloons characterized by re- 

 markable stability of the car, and furnished with screws and rudder, whereby the 

 speed and direction of the balloon are brought, to a certain extent, under the control 

 of the aeronaut ; nevertheless, the great problem of aerostation yet remains unsolved. 

 Some interesting and useful experiments have been made by using captive balloons, 

 by which we have arrived at some facts connected with the upper regions of the air, 

 which could not be obtained by any other means. By means of balloons, valuable 

 meteorological observations have been made at great altitudes in the atmosphere by 

 Mr. Glaisher and other scientific aeronauts. 



JERTTGO. (Verdigris. Acetate and carbonate of copper.) The name formerly given to 

 the bright green rust, produced by the oxygen of the air and carbonic acid, upon copper, 

 and its alloys, bronze and brass. The Komans gave this name ; they considered 

 that the esniqo added much to the beauty of their statues ; and adjusted the compo- 

 sition of their alloys with the view of producing the finest green colour. This was 

 frequently effected artificially; and to distinguish the real from the artificial they 

 used for the former the term cerugo nobilis. This is the patina of the Italians ; it 

 is a form of verdigris. See VERDIGRIS ; COPPER, ACETATE and CARBONATE. 



JETHER. See ETHER. 



JETHIOPS IVZIRTERAXi. The black sulphide of mercury prepared by nibbing 

 mercury and sulphur together. The term Mthiops was applied by the old pharma- 

 ceutical chemists to several mineral preparations of a black or dark colour. 

 ANTIMONIALIS was a sulphide of antimony and mercury. 

 MARTIALIS. Black oxide of iron. 



NARCOTICUS. Sulphide of mercury obtained by precipitation. 

 PER SE. The grey powder obtained by exposing impure mercury to the 

 ar. 



AFFINITY. The term Used by chemists to denote the peculiar attractive force 

 which produces the combination of dissimilar substances as an acid with an alkali, 

 or of sulphur with a metal. See CHEMICAL AFFINITY. 



AFRICAN 1 HEMP. A fibre prepared from the leaves of Sansevieria Zeylanica, 

 a member of the lily order extensively distributed through tropical Africa and 

 India. 



AFRXCA& TEAK. A Valuable wood for ship-building, the produce of Old- 

 fieldia Africana, Bth. t a Wee belonging to the sptirgo order. This wood is to be care- 

 fully distinguished from the true teak. See TEAK. 



ACAXiMATOIiITE. The ' Figure-stone,' or Pagodite, of China ; a soft mineral 

 in which carvings are commonly executed by the Chinese. Under the common name 

 of agalmatolite, are included several minerals similar in physical characters, but 

 essentially distinct in chemical composition. The true agalmatolite is a hydrous 

 silicate of alumina and potash, closely allied to pinite. Professor Brush has shown 

 that certain specimens of so-called ngalmatolito are really a compact form of 



