and on the Minuteness of 'Animalcula. 65 



the two objects above named. Leuwenhoek calculates, pro- 

 bably from conjecture, that the size of some animalcula is to 

 that of a mite, as a bee is to that of a horse. I think that the 

 following observations will demonstrate the truth of that remark ; 

 but in a manner more conclusive and convincing than mere 

 conjecture. 



In the course of last winter, having observed on a dry and 

 frozen gravel walk a variety of small hollows, of a greenish 

 colour, it occurred to me that that tint might have been occa- 

 sioned by the sewn upon water during the summer rains ; and 

 if so, that it would probably contain animalcula. I accordingly 

 scraped off a little of the frozen surface, and mixed it with water 

 which had been boiled, and in which I had previously ascer- 

 tained that there were no animalcula. In a few hours I ex- 

 amined a drop of this water, and found, as yet, no animalcula ; 

 but I discovered a number of minute transparent fibres, appa- 

 rently vegetable, and to the existence of which, the green tint 

 I had first remarked was probably owing. I found these fibres 

 transparent ; and when viewed in a certain degree of shade, 

 I observed them to be marked throughout their whole length, 

 in the most delicate and regular manner, with divisions like 

 globules in a hollow tube, each of which was separated from 

 another by a space of exactly similar dimensions. In the 

 course of a day or two I again examined the water, and found 

 in it a variety of animalcula, some of which were the most 

 minute I had ever observed, except perhaps those found in an 

 infusion of pepper. The highest powers of a good microscope 

 gave me no information as to their form or structure, except 

 that they were of an oval or round form, and moved about with 

 considerable activity. 



Having near me at the time some sea sand which I had 

 been examining, I put a few grains of it into the drop, with 

 the view of forming some idea of the comparative size of these 

 minute creatures ; and I then began for the first time to con- 

 ceive the possibility of what has been stated by Leuwenhoek 

 and others, who have described to us the result of their ob- 

 servations in the minute walks of animated nature. The dif- 

 ference of size, however, was so great, and the angular figure 

 of the grains of sand so rude, that 1 despaired of ever advancing 

 beyond conjecture as to their actual comparative measurement. 



It happened, however, that a straight piece of the above- 

 mentioned graduated fibre lay near one of the grains of sand ; 

 and as the globules or marks in the fibre were as nearly as 

 possible of the same size and shape as some of the animal- 

 cula swimming around, it occurred to me to use this fibre as 

 a base on which to measure the comparative size of the two 



Third Series. Vol. 2. No. 7. Jan. 1833. K 



