



Those cirouinstaaeei have, so Urge a than io the 

 prevention of disease and death, that a thorough 

 of thorn is of vest importaao* to th* welfare of the 



The alatospberic sir, oonsiojered in reference to its nhoniiml com- 

 position, is a mixture of nitrogen and oxygon gases, in fixed and 

 uniform proportion, with carbonic acid aw in a small and variable 

 on. But C|UM to the surface of the earth, it receive* an ad- 

 of partkles or principles of different kinds, by which it is 

 . and rendered 1*** fit for the support of animal and 

 > life. By the respiration of animals, particularly of warm- 

 | *^-" 1 -, as man, a portion uf the oxygen is withdrawn, and a 

 j*"~*ing portion of carbonic acid gas is substituted in it* place. 

 By th* tm*ii*tliin of plant*, th* carbonic acid gas is withdrawn, and 

 an equivalent portion of uajgau substituted. By the mutual action of 

 the sasmhars of th* animal and vegetable kingdoms, the balance of the 

 ssutrtaasBt elements of the atmosphere is maintained. But by a pre- 

 nonserinn* of the member* of either of these kingdoms, an excess of 

 the on* principle and a deficiency of the other will be occasioned. 

 Rence, where there is a huge assemblage of men, the air is less fit for 

 respiration, u happen* in close apartment*: the most melancholy 

 example of this i* to he found in the narrative of the Black Hole at 

 Calcutta; of on* hundred and forty^ix persons confined in thu dread- 

 ful place, on* hundred and twenty-three perished during one night, 

 in plantations suffer more 



place, 

 Tree* cro 



ded 



more from deficiency of 



arbonJo aoid and oxygen, both of which are required for respiration, 

 than from denoiant nutriment by the root* a fact of which proprietor* 

 and manageri of timber-plantations are either not aware, or at least 

 thty neglect th. practice to which it should lead. It may be remarked 

 by ovary one that on the coast, where animal life acquire* an accession 

 of strength from th* parity of the air, which abounds in oxygen, 

 vegetable life languishes from the deficiency of carbonic acid. Iu 

 UMlllmi to that* sources of deterioration, the air in contaminated by 

 various other means, some occasional and limited in their operation, 

 other* mare constant and extended in their influence. A brief review 

 of these will here be proper ; but, before proceeding to enumerate 

 than, it will aflbrd concliuiv* evidence of their importance to adduce 

 one example of the influence of even s alight admixture of a deleterious 

 nrfaapl* with th* ordinary constituents of th* air. " This gas (hydro- 

 chloric acid, or muriatic acid gas) must therefore be very injurious to 

 vegetable life, since so small a quantity as a fifth of on inch, though 

 diluted with 10,000 part* of air, destroyed the whole vegetation of a 

 plant of considerable size in leas than two day*. Nay, we afterwords 

 found that s tenth part of a cubic inch in 90,000 volumes of air had 

 nearly the same effect*." Drs. Turner and Christisou, in ' Brewstor's 

 Journal,' voL vui. p. 145. 



These are principles with the chemical qualities of which we are 

 well acquainted, and the sources of which we can easily ascertain, 

 and often remove ; but there exist other*, of the nature and origin of 

 which far IMS U known, though their effect* are very conspicuous : 

 * are the exhalation* from decaying vegetable matter, termed 

 arsh rsbswists, or malaria, and th* exhalations from the bodies of 

 em sod animal*, when crowded together, or from that of men labour- 

 if under certain diseases, as levers, called the matter of contagion, 

 or fresn dead animal matter, in s state of putrefaction, termed putrid 

 effluvia. These are the fertile sources uf fever*, whatever their form, 

 type, or appellation ; and though it is commonly thought that the 

 fever* from vegetable matter an always of an intermittent or remit- 

 tent character, yet they often astume th* continued form [Aocn] ; 

 while the effluvia from animal matter mostly give riss to fever* of a 

 i Ufa ii 1 1 and typhoid character. (Boot's < Life of Armstrong.') 



What th* nrssise nature of this deleterious principle is cannot be 

 stated, bat whatever it be, when received in sufflcient quantity into 

 the human system, it eeesns to set as a ferment or yeast, sod produces 

 ssriesof changes, th* ultimate object of which is to reduce the body 

 ***ed to s state of putrefaction. We have no test of its presence 

 fcy** M* eibets, but we know the sources whence it spring*, and the 

 cfesuasstsneos which favour it* concentration, sad occasion the human 

 to become more susnpttble of it* influence. It is only by 

 | or lessening these that w can escape thix insidious foe, and 



fiftr 



, 



which ha* attended the enlightened measure* proposed by 

 and chemist* should load to their extended applicati 



. ) 



application. 



Long^ontinuedoahM, in which there I* . stagnation of the sir, and 

 dmf which fresh and purer particles of the atmospheric principle. 

 do not desteud from the higher regions to replace the heated and 

 nentttthiilnl air near the surface of the earth, conduce much to the 

 nsniesKsliuu and virulence of these agents. For several weeks before 

 the plague broke oat fa London, in 1666, there was an uninterrupted 

 calm, so that there was not even sufficient motion in the air to turn 

 VT- A d rt * < fa "Nob th* last plague visited Vienna 

 ts* had been no wind for three month*. To produce agitation in 

 the sir, Ires wore formerly Hghted, and pieces of artillery discharged, 



1 altogether inefficient to cause s ooockUtmbl* commotion in the 



** * large, though a fire U extremely serviceable in renewing 

 t at apartments in house* : the only mean* adequate to this end 

 are beyond our control, though they frequently take place at the 

 asttswW of th* utmost need ; theee are storm* and hurrfcaoes, which, 



however desolating in their immediate effect*, are instrument* of 

 gnat, though less obvious, good. After the hurricane which proved 

 so destructive to the inhabitant* of th* West Indies in 1780, less 

 rliisass occurred than had been known before; even those who 

 laboured under sickness at the time were VmtfltiH by it; fever, 

 diarrhoeas, and dysenteries, but shove all, disorders *~*'"g the lungs, 

 were cured. After the excitation of a storm, plants give out more 

 oxygen, which accounts for the delightful and life-giving freshness of 

 the air, of which every one i* ^mfiN", who walks out into the field* 

 immediately afterwords. 



We may imitate nature, and employ ventilation on s small seal*, 

 but with the best effect*, in our dwelling-places, hospital*, and nick- 

 rooms. The evils of neglecting this salutary measure contrast strikingly 

 with the beneficial consequences of attending to it. It i* remarked 

 by Dr. Macculloch, in his ' Account of the Hebrides,' that while the 

 inhabitants had no shelter but huts of the moet simple construction, 

 which afforded free passage for current* of air, they were not subject 

 to fevers ; but when, through the good intention* uf th.- proprietors, 

 such habitations were provided as seemed more comfortable and .m- 

 modious, but which afforded recesses for stagnating air and impurities, 

 which they hod not the means, or had not a sufficient love of clean- 

 liness, to remove, febrile infection was generated. The mortal fevers 

 which have occurred from crowding human beings together in small 

 ill-ventilated apartment* are numerous. They were termed jail and 

 hiwpital fevers, from their infesting these place. ; the survivors of the 

 night in the Black Hole of Calcutta were, almost without a single 

 exception, attacked by fever ; and the unhappy victims of the mer- 

 cenary actors in the slave-trade were often released from Buffering by 

 the fevers which resulted from crowding so many into a confined 

 space. To avert such calamitous rlinnssns, we must have recourse to 

 measures which will lessen or remove their causes ; such as dispersion 

 of the inhabitants or patients over a larger space ; enforcing cleanliness 

 of the spartmenta and of their persons, and freely ventilating every 

 room. Formerly, in the hospital at Leeds, no patient (suffering from 

 com pound fracture or other severe accident survived, till the ventilation 

 of the wards was improved. One of the most convincing proofs of the 

 different influence of foul and pure air is to be found in the ' Report 

 of the Lying-in Hospital of Dublin.' In the space of four years, ending 

 in 1784, ina badly ventilated house, there died 29 4 4 children out of 7050. 

 But after freer ventilation, the deaths in the same period of time, and in 

 a like number of children, amounted only to 279. The soldiers of our 

 army have been proved to have suffered severely from a like causa 

 through the want of sufficient ventilation in their barracks. Wherever 

 proper ventilation ha* been secured, the building, whether hospital, 

 barrack, or dwelling-house, invariably becomes more healthy. 



Stagnant water, and the mud which remains after it has evaporated, 

 marshes and places occasionally overflowed, emit exhalation* not less 

 noxious than those from decaying animal matter, or the bodies of 

 human beings. These are the more powerful in proportion to the 

 heat ; hence in tropical and warm countries, they give rise to the yellow- 

 fever and the jungle-fever, which are rapid in their course, and generally 

 fatal in their close : in colder countries they produce continued remittent 

 and intermittent fevers. The exhalations are always less hurtful in pro- 

 portion to the activity of the vegetation. The inhabitant* of that part 

 of the town of Batavia which is nearest the mud and slime left by the 

 tide, suffer more from fevers than those who dwell next the marshes, 

 unhealthy as these are. In the marshes of Ante", a great number of dif- 

 ferent kinds of grasses, rushes, Ac., grow, and th* spaces between these 

 plants are covered with large quantities of the Piitia ttratiuta, th* leave* 

 of which float on the surface of the water, and absorb a great quantity of 

 the noxious vapours as fast as they are exhaled, and change them, by 

 the aid of the sun's rays, into respirable air. Thia change i* effected 

 by the plstis more than by any other plant; for it is known from 

 experiments to be so powerful a preventive of decomposition of 

 stagnant water, that if fishes be put into a small quantity of water, in 

 which they would otherwise perish in the course of a few days, they 

 may be preserved alive for a long time by covering its surface with 

 the** singular plants. The utility of a piece of moss introduced into 

 the vase where gold fishes are kept is well known : on this principle 

 di>|K-nds the health of fishes and other animals in the vivaria, now so 

 common; and the lenixn or duckweed, anil th>r plants which cover 

 the surface of ponds in summer, render a similar service to the air 

 here, which the pitia does to that around Batavia. Where marshes 

 cannot be drained, the planting them with marsh and aquatic plants, 

 and such tree* as alders and poplars, is the best mode of mitigating the 

 evils which result from them. The beneficial effects of draining and 

 forming under-ground sewers are shown in the perfect immunity which 

 London enjoys from ague as an epidemic, contrasted with former times. 

 Dr. Caius, the moet eminent physician in England at that period, states, 

 that the mortality of London from ague in 1658 was such, that the living 

 fiiiM hardly bury the dead. 



When these natural means of preventing animal and vegetable 

 exhalations cannot be employed, we must have recourse to artificial 

 means of disarming them of their potency. Of the measures forun .-rly 

 resorted to for this purpose, some were useless, while other* 

 hurtful to the sick, and could not be practised without the removal of 

 the patient*, which can rarely be accomplished. All of them, in point 

 of efficacy and facility ut application, fall short of two agents, which 



