POSSIBLE PASSAGE THROUGH TAIL. 



A grain of mnsk, or a single drop of the otto of roses, will be 

 sensible to the organ of smelling in a large room, and will continue 

 to be sensible for a long period of time. The actual proportion, 

 nevertheless, which the material effluvia producing this powerful 

 effect upon the organs bears to tha total quantity of air impreg- 

 nated with it is quite inappreciable. 



It is pretended by some medical practitioners that the effluvia 

 inspired in smelling certain medicaments is capable of producing- 

 on patients the effects of an aperient, and it is well known that 

 the effects of an emetic are often produced by certain odours. 



Such analogies, therefore, show that the extreme state of atte- 

 nuation, which probably characterises the tails of comets, does not 

 necessarily exclude the possibility of their producing formidable 

 effects upon the organised world, if they should be mingled with 

 the atmosphere. 



7. This supposition has accordingly been adopted by some 

 authors, and among them not a few holding a position of authority 

 in the world of science, as the means of explaining the prevalence, 

 at various epochs, of epidemic diseases. 



Gregory, in a work on Astronomy, published at Oxford in 1702, 

 affirmed that, among all people and in all ages, the appearance 

 of comets has been attended with such general effects; and he 

 adds that it does not become philosophers to treat such traditions 

 with levity, or to reject them, without consideration, as mere 

 fictions. 



So recently as 1829, Mr. T. Forster, an English medical prac- 

 titioner, published a work, entitled "Illustrations of the Atmos- 

 pherical Origin of Epidemic Diseases," in which he professed to 

 prove that, since the Christian era, the periods which have been 

 the most insalubrious have been invariably those at which some 

 great comet was visible. He maintains that the malignant 

 influence of these bodies is not limited to the human race, nor 

 even to the organised world. He ascribes to them innumerable 

 effects upon the inferior animals, and all the violent changes 

 incidental to the atmosphere besides earthquakes, volcanic erup- 

 tions, floods, droughts, and famines. 



Comets appear on the average at the rate of very nearly two 

 per annum. 2Tow, it is generally assumed by the partisans of 

 their influence that they exercise these effects for som-o time 

 before their appearance, and for some time after their disappear- 

 ance. It cannot, therefore, be surprising that those who favour 

 this theory should find a comet for every epidemic or other visi- 

 tation, whether physical, or physiological, which they desire to 

 ascribe to such a cause. 



Nevertheless, frequent as are the appearances of these objects, 



77 



