EPI 



EPI 



ele ; but if upon the concave side, as the 

 difference of the diameters to the semi- 

 diameter of the resting circle. 

 , In the Philosoph. Transactions, No. 

 218, we Lave a general proposition for 

 measuring the areas of all cycloids and 

 epicycloids, viz. The area of any cycloid 

 or epicycloid is to the area of the gene- 

 rating circle, as the sum of double the 

 velocity of the centre and velocity of the 

 circular motion to the velocity of the 

 circular motion : and in the same propor- 

 tion are the areas of segments of those 

 curves to those of analogous segments of 

 the generating circle. 



EPIDEMIC. A contagious disease is 

 so termed that attacks many people at 

 the same season, and in the same place ; 

 thus, putrid fever, plague, dysentery, 

 &c. are often epidemic. Dr. James 

 Sims observes, in the Memoirs of the 

 Medical Society of London, that there are 

 some grand classes of epidemics which 

 prevail every year, and which are pro- 

 duced by the various changes of the sea- 

 sons. Thus, spring is accompanied by 

 inflammatory diseases ; summer by com- 

 plaints in the stomach and bowels ; au- 

 tumn by catarrhs; and winter by inter- 

 mittents. These being obviously pro- 

 duced by the state of weather attendant 

 upon them, other epidemics are suppos- 

 ed analogous to them, and obedient to 

 the same rules, which, on examination, 

 not being the case, all further scrutiny is 

 laid aside, perhaps too hastily. 



The most natural and healthful seasons 

 in this country are, a moderately frosty 

 winter, showery spring, dry summer, and 

 rainy autumn; and whilst such prevail, 

 the wet part of them is infested by vastly 

 the greatest proportion of complaints, 

 but those not of the most mortal kind. A 

 long succession of wet seasons is accom- 

 panied by a prodigious number of diseases; 

 but these being mild and tedious, the 

 number of deaths are not in proportion 

 to the co-existent ailments. On the other 

 hand, a dry season, in the beginning, is 

 attended with extremely few complaints, 

 the body and mind both seeming invigor- 

 ated by it; if, however, this kind of 

 weather last very long, towards the close 

 of it a number of dangerous complaints 

 spring up, which, as they are very short 

 in their duration, the mortality is much 

 greater than one would readily suppose, 

 from the few persons that are ill at any 

 one time: and as soon as a wet season 

 succeeds a long dry one, a prodigious 

 sickness and mortality come on univers- 

 ally. So long as this wet weather con- 



VQL. V. 



i 



tinues, the sickness scarcely abates, but 

 the mortality diminishes rapidly ; so that 

 in the last number of rainy years the 

 number of deaths is at the minimum. 

 The change of a long dry season, whether 

 hot or cold, to a rainy one, appears to 

 bring about the temperature of air fa- 

 vourable to the production of great epi- 

 demics. Some, however, seem more 

 speedily to succeed the predisposing state 

 of the air, others less so; or it may be, 

 that the state of the air favourable to 

 them exists at the very beginning of the 

 change, whilst the state favourable to 

 others progressively succeeds : of this last, 

 however, Dr. Sims is very uncertain. 



Two infectious diseases, it appears, are 

 hardly ever prevalent together ; there- 

 fore, although the same distemperature 

 of air seems favourable to most epidemic 

 disorders, yet some must appear sooner, 

 others later. From observation and 

 books, the Doctor describes the order 

 in which these disorders have a tendency 

 to succeed each other to be, plague, pe- 

 techial fever, putrid sore throat, with or 

 ^without scarlatina, dysentery, small-pox, 

 measles, simple scarlatina, hooping-cough, 

 and catarrh : " I do not mean by this," 

 says he, " that they always succeed each 

 other as above ; for often the individual 

 infection is wanting, when another takes 

 its place, until perhaps that infection is 

 imported from a place, which has been 

 so unfortunate as to have a co-incidence 

 of the two causes, without which it ap- 

 pears that no epidemic can take place : 

 that is, a favourable disposition of the air, 

 and that particular infection. Whenever 

 it happens that one infectious disorder 

 takes the place that should have been 

 more properly occupied by another, it 

 becomes much mom virulent than it is 

 naturally, whilst the former, if it after- 

 wards succeeds, becomes milder in pro- 

 portion : this, perhaps, is the reason why 

 the same disorders, nay, the same ap- 

 pearance in a disorder, are attended 

 with much more fatality in one vear than 

 another." 



EPIDENDRUM, in botany, a genus of 

 the Gynandria Diandria class and order. 

 Natural order of Orchidese. Essential 

 character: nectary turbinate, oblique, re- 

 flex ; corolla spreading ; spur none, 

 There are 124 species. This numerous 

 genus is obscure in its character, differ- 

 ences, and synonyms: for the flowers in 

 dried specimens can hardly be unfolded ; 

 the plants are cultivated in gardens with 

 difficulty ; and the species have not been 

 sufficiently described by authors, who 



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