AIR 



ALG 



without striking their roots into the 

 soil. They usually derive sustenance 

 from other plants. 



AIR PU.MP. A machine for remo- 

 ving the air out of a vessel. The 

 principle of this important philosoph- 

 ical instrument is very simple, and 

 may be easily comprehended from a 

 brief explanation. The essential part 

 ,| ofthe machine con- 



,J\ sistsof an exhaust- 



i-q /T^ ing syringe (a), 

 formed of a tube 

 or barrel of brass, 

 closed at one end, 

 with the exception 

 of a small orifice, to which a valve 

 (A), opening inward, is attached. An 

 air-tight piston is worked up and 

 down in the barrel by a rack and pin- 

 ion turned by a winch. The piston 

 has also an orifice with a valve (c), 

 which opens upward, or in the same 

 direction as the valve of the tube. 

 The syringe communicates, by means | 

 of a small pipe {d) fitted into the open- 

 ing at its lower extremity, with a ves- 

 sel (e) called the receiver, from which 

 the air is to be extracted. 



The receiver is placed on a brass 

 plate ( f, g), over a small hole, into 

 which the other end ofthe pipe is in- 

 serted ; and, in order that the contact 

 may be air-tight, the edge ofthe glass 

 is previously rubbed with lard or some 

 unctuous matter. 



Suppose the piston at the bottom 

 of the tube. As it begins to be drawn 

 up, the valve c ofthe piston is imme- 

 diately shut by the pressure ofthe ex- 

 terior atmosphere, so that no air can 

 enter the barrel, and a perfect vacu- 

 um would be left under it, were it not 

 that the valve at the bottom of the 

 barrel is forced open by the pressure 

 ofthe air in the receiver, which rush- 

 es into the barrel till its density be- 

 comes the same both in the receiver 

 and barrel. When the piston has been 

 drawn to the top of the barrel, the 

 whole of the air which occupied the 

 barrel has been removed, and the re- 

 ceiver and barrel are now both filled 

 with the air which was previously 

 contained in the receiver alone. — 

 {Brandcs Encyclopedia.) 



Spiral vessels, 

 With 



AIR VESSELS. 

 tracheae. 



ALATE (from ala, a icing). 

 lateral expansions, winged. 



ALBU.MEX. One of tlie important 

 azotized principles of animals and 

 ' plants. In the solid state it consti- 

 ' tutes the principal component of 

 membranes, and in the fluid form is 

 found in the serum of blood and the 

 white of egg. The juice of all plants 

 contains a small quantity. In the 

 moist state it is readily putrescible, 

 and coagulates at about 180° Fahren- 

 heit ; but when dry it is a transpa- 

 rent, brittlfe substance, which resists 

 decay. For its composition, see Pro- 

 tein. 



Albumen, in botany, is the fleshy, 

 mealy, or horny substance forming 

 the substance of the seed, and lying 

 between the embryo and testa. 



ALBURNUM. The sap wood. 

 The ascending sap rises along its 

 pores. It is usually of a different 

 colour, and much more perishable 

 than the heart wood. 



ALCOHOL. Spirit of wine. It is 

 formed during the vinous fermenta- 

 tion. The pure spirit has a specific 

 gravity of .792, and consists of C^ He 

 0:. It is present in brandy, whiskey, 

 and strong spirits to the extent of 

 fifty per cent., twenty-five per cent, 

 in strong wines, ten per cent, in ci- 

 der and ales, and six per cent, in beer. 

 It is of great use in the laboratory as 

 a solvent of resins, &c., and for the 

 hot flame it produces when burned in 

 lamps. 



ALDER. Shrubs of the genus ylZ- 

 nus, which is closely allied to the 

 birch. The common swamp alder is 

 the A. serrulata. The A. glauca (black 

 alder) is used by dyers for the produc- 

 tion of a black. 



ALE. A strong beer made from 

 light malt. 



ALE-HOOF. Ground ivy. 



ALEMBIC. A retort with a move- 

 able cover or cap. 



ALEXANDERS. An umbelliferr 

 ous plant, formerly cultivated like 

 celery. 



ALG^. The family of sea- 

 weeds and fresh- water weeds (Co/i- 

 ll 



