1865.] On the Predisposing Causes of Pestilence. 381 



differences in the distribution of partial light and shade on Venus, 

 before sunset, as to give some reason for hope that it was not all 

 cloud-land which was surveyed with the long telescopes of Cassini. 



The rotation period of Venus was given by Cassini at 23h. 16m., 

 and by Schroter at 23h. 15m. 



Of the surface of Saturn, we have, chiefly, belts like those of 

 Jupiter, but not so clearly denned ; some spots from which the 

 rotation has been computed at lOh. 16m., and some variable appear- 

 ances about the poles which indicate atmospheric changes ; for we 

 dare not speak of polar snows in so distant a planet. 



The observations on Jupiter, in some degree intermediate in 

 character and in distinctness between those of Mars and those of 

 Saturn, help to confirm the now general belief in the common origin 

 and agreeing nature of all the planets. For here spots of a definite 

 shape and place are traceable in the dark spaces between the bright 

 belts ; the belts are seen to change in extent and outline ; they vary 

 even in number, and are constant only in the direction parallel to 

 rotation, and in the colour, which is that of cloud reddened by 

 morning or afternoon sunshine, and this not equally in every part. 

 The rotation is accomplished in 9h. 56m. This prodigious velocity, 

 about 30,000 miles an hour at the surface, would have occasioned 

 heavy cyclonic storms, and violent winds from the north-east and 

 south-west, but for the nearly perpendicular position of the axis of 

 the planet to the plane of the orbit — a circumstance also observed in 

 Saturn, and productive of the same regular atmospheric currents. 



ON THE PKEDISPOSING CAUSES OF PESTILENCE. 



There are many persons to whom the existence of disease is the most 

 mysterious and inscrutable problem in Nature ; who regard it as a 

 phenomenon the most difficult to reconcile with the wise government 

 of an all-merciful Deity. Such persons, along with others who do not 

 trouble themselves to think at all, regard the advent of a pestilence 

 with superstitious fear, as did their ancestors, considering it to be a 

 scourge sent to punish man for his spiritual backslidings ; his sinful- 

 ness often consisting, in their eyes, of a disbelief in, or neglect of, 

 their particular views of salvation. Those, on the other hand, who 

 are often derisively called optimists, look upon physical maladies as 

 civilizing influences, having their origin in the neglect, not of spiritual 

 but of moral and physical laws ; and although they, too, fear the 

 approach of a plague, it fails to awaken in them a superstitious and 

 inexplicable dread, but calls forth renewed activity in the work of 

 sanitary reform. A more pressing duty prevents us from entering 

 further upon the philosophical consideration of the subject, but it will 

 be found that what has been said of the present applies also to the 

 past, and that the nature and predisposing causes of disease have 

 always been similar to those which prevail in our time. 



