Ill 



AttKIAL IMAGES. 



AtKO-DYNAMICS. 



cambium with the sulphuric ; so that, instead of sulphuric cid and 

 carbonate o( soda, we obtain carbonic acid and sulphate of soda. The 

 carbonic acid assumes the gaseous form, and ascends to an earthenware 

 vassal in the upper part of the apparatus. This iinniil contains water ; 

 nod aa the apparatus is kept oscillating, the water is sufficiently 

 agitated to absorb the gas passed up into it. With a small apparatus 

 capable of holding a gallon at a time, a quarter of nn hour's oscillation 

 will suffice to impregnate the water with gas to a pressure of five 

 atmospheres. The apj>aratus must of course be strong to resist this 

 pressure ; it is made of iron, and there is a pressure gauge at the top, 

 to measure the amount of the pressure. There is a tap for draining off 

 the aerated liquids. Dr. V enables states that for a gallon of water to 

 be impregnated to the extent of fire atmospheres, would require about 

 six ounces of carbonate (or rather seequi-carbouate) of soda and foul- 

 ounces of sulphuric acid. The apparatus admits of being used in many 

 ways ; for tin- aerator or upper vessel may be cither tilled with pur* 

 water, and modified only l>y the gas which ascends from the generator, 

 or the water may previously be made acid or alkaline, and receive a 

 further change l>y tho aeration. The resulting beverage will thus 

 depend, not only on the aeration, but also on the state of the water 

 before aeration. 



Numerous other machines have been introduced for making and 

 bottling soda and other aerated waters. Messrs. Cooper and Bursell, 

 Messrs. Mayo, Mourn. Tylor and Son, Messrs. Tyler and Hayward, 

 Messrs. Masters, and Mr. Cox, are all patentees of apparatus of this 

 kind ; and M. Savarease and other manufacturers in France have dis- 

 played their ingenuity in a similar direction. The first-named manu- 

 facturers have patented an aerating machine and a carbonating machine, 

 adapted to the manufacture of aerated waters. Messrs. Mayo's patent 

 biphon vase, for containing aerated waters, and made by a combination 

 of metal and pottery, affords the means of withdrawing at pleasure 

 such quantity of the beverage as may be required, and keeping 

 the rest in a state fit for effervescence. Messrs. Tylor and Son have 

 invented a small fountain soda-water machine, a double soda-water 

 machine (with a gasometer similar to those used in gasworks), and a 

 tattling or corking machine. Messrs. Tyler and Hayward have a 

 double soda-water machine for two bottles, capable of making 300 

 dozen per day. 



There are two or three of these machines which deserve a little 

 attention for the ingenuity displayed in them. In Cox's apparatus the 

 impregnating gas may be sustained at a pressure sufficient to cause its 

 absorption by the liquid to be aerated without the aid of force-pumps. 

 The machine can aerate 50 gallons in an hour. There is a vessel called 

 a generator, in which lime-water is placed ; another vessel containing 

 dilute sulphuric acid ; a third vessel, the purifier, containing water ; 

 and a fourth, containing the liquid which is to be aerated. The acid is 

 admitted into the generator, where it is kept agitated or stirred with 

 the lime-water ; carbonic acid gas is formed by the decomposition of 

 the lime, and is admitted into the purifier, where it is cleansed from 

 some of its impurities by passing through the water ; the gas then 

 passes into a cylinder containing the liquid to be aerated, where a 

 constant agitation is kept up to facilitate the aeration. The gag is 

 generated under such circumstances as to give it an intense pressure, 

 which renders necessary great strength in the apjiaratus. There are 

 contrivances in the cylinder for facilitating the bottling of the aerated 

 liquid. 



Messrs. Marten's aerating apparatus is very simple in construction, 

 Mid is adapted for domestic rather than for manufacturing uses. It 

 consist* of two globular-shaped glass vessels, the upper one of which 

 receives the water to be aerated, while the lower is that in which the 

 gas is generated. The machine can hold about liquid enough for six 

 ordinary tumblers or goblets. To make soda-water, the upper globe is 

 tilled with the pro|x.T liquid, and the materials for generating carbonic 

 acid are introduced into the lower ; there is a connection between the 

 two globes, which are in other respects air-tight. The aeration or car- 

 bonating is speedily effected, and the soda-water can then be drawn off 

 at pleasure by means of a patent siphon tap worked by a spring. Any 

 kin.lt of beverage, such as wine, lemonade, nectar, ale, beer, Ac., can be 

 brought into an effervescing state in a similar way; and the ready 

 minis in which this is effected constitutes a recommendation of the 

 machine. 



M. Naval-esses machine aerates from 300 to 3000 bottles per day, 

 according to its wan. It is intended for the aeration or effervescing of 

 drinks generally ; it is somewhat complex in arrangement, but can be 

 worked by one person. Belonging to but detached from this is a vessel 

 called . H ,*nid. to transfer the aerated liquid to a glass ; the siphoid is 

 tilled from the large machine, and may then be emptied by glassful* 

 without any deterioration of quality. 



Menwu. Knight patented an air-tight U>P|MT in 1844, for flasks 

 intended to contain the aerated water, when required to keep it some 

 tim- for further operations, or to transfer it to the common glass- 

 bottle*. It U an ingem'nim piece of ap|ratus, xtrong enough to resist 

 the rxpuuive force of the gan, yet easily adjusted for the entrance or 

 exit of liquids. 



AttKlAL I MAG KM is a term applied to those image* v. hi>h arc 

 caused by the convergence of reaeoted or refracted rays of light, when 

 they appear to be suspended in tho air. [ Limit ; MIHAGK.] 



itftlAL PEKSl'KiTIVK, a term in ,intin*. implies, in iU 



simple definition, the receding of objects into distance, as seen through 

 the medium of air. lu iU general application, however, it is to be 

 understood in a more enlarged sense. Linear perspective may be con- 

 sidered the material guide of the artist, originating in, and governed 

 by, mathematical science ; but aerial perspective u, in whatever 

 relates to tfect, amenable to no positive law or established ml 

 depends for its application on tin- perceptions and capacity of the 

 artist. Although entering into every variety of subject, in graphic 

 representation, it is in open scenery that aerial perspective is exi 

 in its proper sphere. To feel this, it will only be necessary to recol- 

 lect in how different an aspect the same scenery may present itoelf 

 under different modifications of the atmosphere. A pruepect, which 

 at noon day, or in a clear and bleak morning, appears tame and unin- 

 teresting, will often assume an ideal character, and start into combina- 

 tions of beauty, if seen at sunrise or at sunset, or under tho influence 

 of any atmospheric phenomenon favourable to the developtu 

 picturesque effect. 



It is, of course, in those schools of painting, wherein the .-i 

 external nature, especially of landscape, baa been most cultivate 

 we are to look for the finest examples of aerial perspective. Tl,- 

 Roman and Florentine masters, whose object, almost exclusively, was 

 human form and character, seem to have felt or understood but little 

 of it. The Dutch and Flemish jiainters exhibit very considerable 

 excellence ill this particular, as i* shown in the works < i I: 

 Kcmbrandt, Cuyp, Kuysdael, &c. Franer, however, lias the gl 

 having produced the artist Claude Lorraine, who, in this great quality 

 of art, bore off the palm from all competitors. He rarely painted any 

 "thrr eH'cct.-. than those of the rising or the setting sun ; but \\h 

 be his subject, an ancient port, or ruins, or temples, the great and 

 presiding charm of Claude is his consummate skill in aerial pri--i 

 but the aerial perspective of a calm and placid .itm-|>)i< n . It then 

 be any of the older masters who. in the treatment of aerial l>er-| 

 can compote with Claude, that comi^titor, ]>crlia]>s. is t'ujp. Hi 

 pictures are direct portraits of the scene before him, tho willowy lake, 

 the marsh, the meadow, the drowsy shepherd, and tho rum in.it i i 

 lint, iii spite of the simplicity of these materials, and an hoi i 

 general, perfectly flat, he communicates to his works an effect 

 and distance, and consequently of reality, which must rank them 

 the most remarkable efforts of art. To these may IKS added tin- Knirli-li 

 Wilson, whose mastery in the practice of aerial perspective, give* him .> 

 right to rank with Claude and with Cuyp in this quality : ami Turner, 

 whose representations of a wide expanse of country under the iiitlueii. e 

 of atmospheric phenomena, are unequalled by any painter, ancient " 

 modern, for the almost unlimited variety of their range, and the 

 brilliancy and accuracy of their aerial effects. Indeed, in his nnnibri- 

 less oil paintings and water-colour drawings, nearly every vai 

 aerial effect, from the calmest and most unruffled sky to the i 

 tempest, may be found represented with the most surprising force and 

 fidelity allowance being made for occasional exaggeration of colour 

 the accurate perception of the relative distances of the various objects, 

 and whatever is understood under tho term aerial perspective bcinc 

 still strictly maintained. 



A KHO- DYNAMICS, signifies the science which treats of the motion 

 of the air, or of the mechanical effects of air when in motion. In it, 

 widest sense, it might be token to include the effects of the motion 

 of any gaseous substance or vapour ; and even the properties of 

 might be considered as a part of the science. We shall however < ..n 

 fine ourselves to the explanation of the few general principles win. h 

 can be relied upon, with regard to air ainnr, leaving the other- t"i 

 their proper places, with their chief applications, such as ANKMOMKTKII, 

 WIND-MILL, Aiu-ci N, SAIL, STEAM-F.XOINK, RESISTANCE, GTNNKIIV, &<. 



If there be one part of dynamical science more abstruse 

 another, it ia the doctrine of the propagation of motion in fluid-, 

 especially elastic fluids, like the air. In this case, the acting 

 may be said to consist (1) in local dilation of part* of the atn>".-|>hcic 

 by the sun's heat during the day, and contractions by cold during the 

 night; (2) in the permanent difference in temperature of the 

 tonal and polar regions; (3) in evaporation from some parts of tic 

 earth's surface, by which the air, being entangled, so to speak, in the 

 meshes of the vapour, is displaced upwards, and in condensation a- 

 rain. Ac., in other parts, by which air is carried downwards with a 

 large quantity of transferred latent heat ; (4) in the effect of the <livci . 

 sitiee of land and sea, mountains and valleys, lakes and river*, all of 

 which forces act so aa to cause motion in the aerial ocean ; (6) in the 

 rotation of the earth on its axis. Vapour introduced into the air by 

 evaporation acts as a moving power in fioo ways: (1) By a simple 

 addition of volume. The tension of the vapour is, by Dalian's law. 

 added to the elastic force of the air. (2) Since va|>ur of water i 

 less specific gravity than air, in tho ratio of rrO'j:>."i : 1. leh 

 lightest of vapours, and, except hydrogen and ammonia, the licjr 

 gases, its upward diffusion is much more rapid than it* boricontal, and 

 acts in producing ascensional motion in the air h 



The dilatation of the air by heat acts rather dilt.-i. ntl\ Air i- on!;, 

 dilated by ,'nth of it bulk by an increase of fiO K, so that 

 producing up-rushing current* is very small, unlem it be v. 

 heated. It, however, acts chiefly by upheaving the superincumbent 

 strata, and causing them to flow over on other cooler regions. For 

 aerial motions caused by the earth'" rotation, we WINK TH.MU: w IM. 



