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disease are communicated by drains and sewers from 
house to house, and that untrapped or badly trapped ones 
are far worse than having no drains at all. 
“On a new Theory explanatory of the Phenomena exhi- 
bited by Comets,” by David Winstanley, Esq. 
An explanation of the phenomena exhibited by cometary 
bodies seems to have been generally sought for amongst the 
most hidden of nature’s operations, indeed inventors of 
theories would appear to have taken it as an axiom that the 
extraordinary and imposing aspects which are frequently 
presented by the heavenly bodies in question can only be 
explained by the operation of natural laws which here we 
do not know, by the existence of chemical substances which 
here we have not got, or by the presence elsewhere of con- 
ditions which here we do not find. To me it does not seem 
that the causes of cometary appearances are of necessity 
deeply hidden, nor that the invention of new natural laws, 
new chemical substances or new conditions of matter offers 
us a more philosophical or even a more handy means of 
accounting for those appearances than without them we 
already possess. 
It is undoubtedly in the presence and the configuration 
of their tails that we recognise the greatest visible differ- 
ences from the planets which comets exhibit. But these 
visible differences curious and interesting as they are when 
present are sometimes wholly wanting, ofttimes merely 
rudimentary, and when existing are continually altering 
their dimensions and their forms. There are, however, two 
points in which comets constantly differ from the other 
members of our system, and these points are to be found in 
