Observations on Donates Comet of 1858. 445 



Another class of heavenly bodies move — revolve in orbits like 

 that of our earth — round the common centre of our system^ the 

 sun. The limits and courses of these wandering bodies, the night- 

 watchings of the astronomer have pencilled and measured as with 

 a span ; he has also weighed them as in a balance. A very few 

 years ago the number of these bodies — the planets — did not ex- 

 ceed five, but recently the catalogue has increased to sixty-one; and 

 but a few years have passed away since Leverrier, as with a colos- 

 sal stride, placed one foot as it were on the centre of the sun and 

 the other on the surface of the remotest star of our system, and 

 pointed out the spot where a new planet — Neptune — was to be 

 found : such has been the modern progress of science. 



At certain periods of the world's history another class of erratic 

 bodies, called comets, have appeared in the celestial vault, whose 

 perihelion passage was in comparatively close proximity to the 

 orbit of our earth, while its aphelion circuit far exceeded the im- 

 mense distance of those remote stars already mentioned. Bodies 

 of this nature in all ages of the world have attracted the attention 

 of astronomers, and filled the wondering inhabitants with awe and 

 amazement, appearing for a few nights, and even at noon-day, with 

 excessive splendour, and then apparently vanishing into the depths 

 of space for ever. The written history of the appearance of comets 

 has always been associated with some disaster, hence the popular 

 fear at their appearance. (I need only call to recollection the 

 panic which spread over the United States and the Continent of 

 Europe last year.) 



The description of the appearances of these bodies has often been 

 distorted by the fears of the historian and the excited imagination 

 of the ignorant. So far back as 596 years before Christ, the 

 mother of the Chinese Emperor Yu, considered the comet of that 

 year as auspicious for the future Empire and the yet unborn Em- 

 peror ; but modern astronomy has robbed these bodies of their 

 terrors, and they are now considered as forming a part of our 

 solar system, and appearing at certain intervals of time. To 

 trace the orbits of these bodies and predict their return involve 

 calculations of no small labour. Their light density subjects them 

 during their circuit to perturbations from all other bodies which 

 can act upon them, and so deflects or retards their course : hence 

 the difficulty in predicting their return. But here again science 

 Las once more triumphed, and a Hal ley, a Biela, and an Encke 

 have traced their orbits, measured their distances, predicted their 



