MEMOIR OF SWAMMERDAM. 33 



ceive," (alluding to the minuteness of fern seeds, and 

 the mechanism employed to disperse them,) (f with 

 what rapidity they may be wafted ahout by the wind, 

 so as to account for these plants being found on the 

 tops of the highest trees, and on walls, wherever 

 they can find mould enough to take root in. 



" The great obscurity of the human understanding 

 is clearly proved by this observation, for, if it were 

 not very dark indeed, how could it, during so many 

 ages, deny that this plant had either seeds or flowers ? 

 insomuch that it was one of the first errors taught 



o 



young people in books, as well as heard in conversa- 

 tion. We ought, therefore, to thank the Sun of 

 divine grace, and true fountain of all useful know- 

 ledge, that we are at last so happy as to attain more 

 just notions of this matter. Should not this mistake 

 teach us modesty in our opinions and our judgment 

 upon many other occasions, seeing upon this the 

 most penetrating geniuses have all gone astray ? If 

 we are so liable to mistakes in regard to things that 

 lie open to our inspection, what are we to say of our 

 opinions of things that are invisible? How many 

 idle- notions are formed on such subjects ! how many 

 senseless conceits, with which, however, we sometimes 

 suffer ourselves so far to be deluded that we make 

 nothing of injuring, both in character and person, 

 those who happen to be of a contrary opinion ! It is 

 therefore, absolutely necessary that we should always 

 distrust ourselves and a:t with the greatest circum- 

 spection. In our present wretched condition, we 

 are surrounded with ignorance on every side, and 



