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of credulous belief,—used to argue that there had been aninfinite series of men upon earth ; and, of course, if the racehad no beginning, could it be held in consistency that it wasto have an end ? We now absolutely know, as geologists,not only that a beginning there was, but that the beginningwas a comparatively recent event; and further, founding onthe unvarying experience of the past, we also know that therace, in at least its existing character and condition, is tohave an end. There are peculiarities, too, in the visitationsof the present time, suited to suggest many a pregnant thoughtin connection with this curious and surely not unimportantsubject. I travelled by railway, in middle autumn, two yearsago, for about a hundred miles, through a series of well-cul-tivated fields j and found almost all their potatoes, constitut-ing about one-fifth of the entire produce of the district, killedby a mysterious disease, and exhaling a heavy odour of deathand decay that infected the air mile after mile. There wereperhaps as many individual plants of this useful vegetablelying brown and dead in the extensive area through which Ipassed as the entire species would have consisted of had itnot been so sedulously and extensively cultivated by man;and the appearance of the blackened and fetid fields suggest-ed to me how, in at least some of the instances, species mayhave died. A disease similarly extensive is devastating atthe present time the vineyards of the south ; and it is saidthat, should it continue its ravages for a year or two longer,the generous Madeira of the wine-drinker will become asmuch a mere tradition in consequence as the extinct winesof the ancients. Nay, during the present age have we notseen a new and terrible disease, quite as mysterious in itscharacter and origin as any of those which have fallen on thevegetable kingdom, sweeping away greatly more than a hun-dred millions of our own species ? Read in the light of geo-logic history, with its irrefragable evidence of the often-it*