n 



A8PKRTAXVIC ACID. 



ASPHYXIA. 



they are in 

 are used. 



N m \-.- 



I : :....: 



tactile 

 Quartil* 



; 

 1 ' 



The following are the 'character, which 



1 : 



0* 



no* 

 ISO 



D 



* 



ASPERTAX N 1C ACID. An acid Mid to be found in sweet-Mental 

 woodruff (AaxrtJa odorala\. Ite exitnce i* doubtful. 



ASPHALT. A solid bituminous or resinous substance found on 

 the shores of the Dead Sea, in Trinidad, and in other localities. It U 

 doubtless of rentable origin, and U probably produced by volcanic 

 actiun upon coat-bearing strata. It U generally black, and more or 

 lea* lustrous, like pitch, with which, in fact, asphalt poweMes much 

 umiUritr. Oil of turpentine diiwolves out of it a black substance, 

 which U insoluble in alcohol and ether, and to which Boussingault has 

 given the name Aipkalti* ; ite composition is expressed by the formula 



AS^HALTE. The uae of street-pavement* formed of agphaltic or 

 bituminoua compound!, and especially of that commonly known as the 

 acphalte, or aaphaltic mastic of Seyssel, was introduced into this coun- 

 try by Mr. CUridge, under a patent obtained in 1837. The progress 

 which such pavement* have made in public favour within the last few 

 yean haa been lea* than was at first anticipated. While however com- 

 paratively little ha* been done in the application of asphalte to street- 

 pavement*, it haa been brought somewhat more extensively into use 

 for foot-pavement* in leas exposed situations, such as the platforms of 

 rail way -stations, for flooring, roofing, and protecting buildings in various 

 ways from injury by damp. 



The principal ingredient of the Seyssel asphalte is a dark brown bitu- 

 minous limestone, found near the Jura Mountains. This stone is broken 

 to powder and mixed with mineral tar and sea-grit ; and the whole is 

 rrfnftA for several hours to a strong heat in large cauldrons, until the 

 ingredient*, which are continually stirred by machinery, ore perfectly 

 united. The mastic U then run into moulds about eighteen Aches 

 square and six inches deep, so as to form it into cakes or blocks 

 weighing from 122 Ibs. to ISO Ibs. each. In this state the asphalte is 

 delivered for use, and portable furnaces and cauldrons are provided for 

 re-melting it upon the spot by fires of wood or coke. In this operation 

 1 Ib. of mineral tar is first put into the cauldron or boiler, to which, as 

 oon aa melted, 56 Ibs. of mastic, broken into pieces of not more than 

 1 Ib. each, are added, the whole being stirred together. The cauldron 

 U then covered over, and a brisk fire kept up for a quarter of an hour, 

 after which 66 Ibs. more of mastic are added and stirred in. The 

 cauldron is again covered for a few minutes, and further quantities of 

 tar and mastic are added, in the proportion of 1 Ib. of the former to 

 112 Ibs. of the latter, until the cauldron U full, and the whole is com- 

 pletely melted and fit for use. For some purposes the proportion of 

 the ingredients is different from that above-named. 



In laying foot and carriage pavements with asphalte, there is a neces- 

 sity for securing a firm, solid foundation, which, whenever the ground is 

 oft, must be accomplished by ramming, or by removing the soft earth, 

 and substituting a coarse concrete of gravel and pounded lime-stone. 



The mode* of applying asphalte to the pavement of cellars and base- 

 menu for the purpose of excluding damp, vary according to circum- 

 stances. When water is liable to rise under the floor, a brick invert, 

 hid in asphalte as a cement, should be adopted, us the simple 

 pavement laid on concrete will not prove effectual Damp may be 

 effectually prevented from rising in wails by forming the whole of one 

 horizontal joint a little above the ground level with mastic in lieu of 

 mortar ; and skirtings of asphalte, which are formed by pouring the 

 mastic into iron moulds applied to the wall, and assisting its descent 

 with the spatula, may in some cases be applied with advantage. In 

 covering upright surfaces asphalte is not so applicable as in other 

 cam, sine* it will not bear exposure to the heat of the sun, and will 

 not adhere well to a damn, dirty, or soft surface. 



Boofa, especially if of flat pitch, may be advantageously covered with 

 fin* asphalt* laid upon a thin coat of fine concrete, supported by a 

 rough boarding of dry wood. 



Tne thickness of asphalte used for pavemenU varies from half an 



men to about an inch and a quarter, the former being sufficient for 



common floors and court-yards not intended for carriages, and from 



three-quarters to an inch being the least allowed for carriage pave- 



moots ; from half an Inch to five-eighths is sufficient for roofs and the 



covering of arches to prevent the nitration of water, and for the lining 



Unks and poods; and about half that thickness is sufficient for 



ring the ground-line of brick-work, to prevent the rising of damp. 



II attempt* to employ asphaltto pavement* for the foot-way or 



iTtage-way. of the London street* have failed ; the traffic subject* 



i to a w*ar and tear greater than they are fitted to bear. Con- 



abb outlay wi* incurred in the trials made by the various 



pariabe. and paving cotnmiauonen ; so complete has been the failure, 



njr, that at Ib. present tim* (186) scarcely an example of 



aupbaltio foot and carnage pavement can be met with in the mc- 



tropoli*. 



A useful recent application of aaphalto is, a* one component of the 

 ' patent asphalted felt,' employed for roofing, aheaUiing, and other pur- 

 IIIMSS Ite inventors chum for it the propertie* of impermeability by 

 rain, non-conduction of heat, resistance to vermin, lightness, economy, 

 and durability. Beside, roofing and sheathing, it is intended to be 

 applied for lining granaries and store*, clothing or < jacketing ' steam 

 pipes and boiler*, and forming a ban* or ground for paper-hangings on 

 damp walla. The felt is formed of any refuse fibrous material satu- 

 rated with melted asphalte. 



The no-called asphalte used in the construction of pavement, is chiefly 

 pitch the residual product of the distillation of coal-tar. 



ASPHALTIN. [ASPHALT.] 



ASPHYXIA, a Greek word (lur^ta) which signifies a cessation 

 of the pulsation, originally expressed any state of disease in wliii-h 

 there was a suspension or loss of the heart's action, and a consequent 

 failure of the pulse ; but the term i* now used to denote a condition of 

 the system in which there is a cessation of muscular movenn 

 arrest of the circulation, and an accumulation of blood hi the veins. 

 The state of asphyxia is that in which the respiratory actions are 

 either temporarily suspended, or have wholly ceased ; a state neces- 

 sarily inducing such a change in the nature of the blood as U 

 incompatible with the continuance of life. The blood which circulates 

 in the two great systems of blood-vessel*, vein* and arteries, is ess an- 

 tially different [BLOOD, NAT. HUT. Div.] ; that in the vein* is incapable 

 of supporting life ; that in the arteries U the proper nutrient and 

 excitent of the system. The object of respiration is to convert venous 

 into arterial blood. Of all the conditions necessary to the action of 

 the vital organs, that of receiving a due supply of arterial blood is the 

 most indispensable. If a ligature be placed around the trachea (wind- 

 pipe) of an animal, so as completely to prevent the access of air to the 

 lung, and if at the same time the carotid artery be opened, that is, one 

 of the great arteries which springs from the arch of the aorta [HKART, 

 NAT. HIST. Div.], and which, passing along the neck to the head, is 

 the main channel through which the brain receives it* supply of 

 arterial Hood, it is found that in a definite time the blood flowing in 

 this artery has ceased to be arterial, and has become venous. Taking 

 the average of a great number of experiment* performed on dogs, for 

 the express purpose of ascertaining this fact, it ia found that, in about 

 three-quarters of a minute after the complete exclusion of air from the 

 lung, the blood in the carotid artery begins to lose ite vermilion colour. 

 After a minute and a quarter, it has become obviously dark ; in tin- 

 space of a minute and a half, no difference whatever can be perceived 

 between the blood that flows from this artery and ordinary venous 

 blood; in this space of time, therefore, the system of an aniiua! 

 whose lung air is excluded, is brought completely under the in!' 

 of venous blood. 



While the blood is thus changing from arterial to venous, the function 

 of the brain is greatly affected. Sensibility diminishes as the blood 

 darkens ; and when it has become quite dark, the power of senaation in 

 wholly abolished, and the animal lies in a state of profound coma. 



The influence of the circulation of venous blood upon the muscular 

 system is no lees powerful than that upon the the nervous, for the 

 muscle can no more perform its function without the stimulus of 

 arterial blood than the brain. When, in consequence of the exclusion 

 of air from the lung, venous blood is sent out to the system, the heart 

 is always the first muscle that feels the effect of this abstraction of it* 

 accustomed stimulus; because venous instead of arterial blood ia 

 instantly brought into direct contact with the surface of ite left 

 cavities [HEART, NAT. HIST. Div.], and because venous instead of 

 arterial blood is sent by its nutrient arteries (the coronary, which are 

 the first branches given off by the aorta) into its very substanci 

 this blood, a* haa been already stated, is incapable of affording it the 

 requisite nourishment and excitement Accordingly the action of tin- 

 heart is always greatly affected from the very first moment that an 

 animal is brought under this condition. At first, it* contractions are 

 somewhat accelerated, probably on account of the violent struggle* of 

 the animal, and in consequence of the emotion of fear ; but in a few 

 seconds it* action begins to be arrested, and it becomes rapidly less 

 and leas frequent until it sinks to a point surprisingly low. When in 

 a state of health and unexcited, the pulse of a dog is 130 in a minnt.- ; 

 but in two minutes after the exclusion of air from it* lung, it sink* 

 to 25, and it often falls still low, r. Immediately before death it 

 invariably becomes again accelerated, sometimes rising to ite natural 

 standard ; but what it then gains in velocity it loses in strength, and 

 in all cases within three minutes after the complete exclusion of air 

 from the lung, the action of the heart ha* become feeble ; this feeble- 

 ness gradually but rapidly increases, until at the end of the : 

 minute it is seldom that the action is at all perceptible by the finger. 

 But though the heart be the first to feel the effect of the abstraction 

 from the system of ite usual stimulus, yet the blood which is trans- 

 mitted to all the other muscle* of the body is alike incapa'' 

 exciting them to contraction : the muscles of respiration suffer with 

 the rest, so that the respiratory movements, that is, the alternate 

 enlargement and diminution of the cavity of the chest, indispensable 

 to the entrance and exit of fresh current* of air, cease. Not only is 

 the muscular system thus affected, but the capillary system has at 

 last ite action suspended, and no more blood passe* from the arteries 

 to the veins, and the venous system is greatly congested. 



