28 



HARDWICKE'S SCIENCE-GOSSIP. 



position in the tree, and by means of which its bulk 

 or thickness is daily increased. These vessels are 

 of two sorts ; one sort of these horizontal vessels, 

 which originally, or at the first formation of the 

 plant, are derived from the marrow or pith in the 

 centre of it, but afterwards in great numbers take 

 their origin from the perpendicular vessels. 



" These vessels appear to my eye like dark streaks 

 (when seen in a transverse section), but, in order to 

 examine them more closely, I cut a piece of wood 

 lengthwise, so that they were cut exactly across, 

 and then each of them appeared to be formed of 

 five, six, or even seven vessels joined one to another, 

 and intermixed among the perpendicular vessels. 



" The other sort of horizontal vessels lie in great 

 numbers or clusters closely joined to each other, 

 though not evenly diffused through the wood." 



Leeuwenhoek's figure represents a series of 

 elongated cells, and he says, " I have in many 

 places drawn cross-lines to represent what I con- 

 ceive to be minute valves, and although I could not 

 see them so distinctly as here they are drawn, yet I 

 cannot doubt of their existence, having frequently 

 seen these valves in other woods, and particularly 

 very distinctly in the elm ; besides it seems very 

 evident to me that without such valves the tree 

 could not be increased in bulk on account of the 

 great force required to separate and loosen the bark 

 from the tree in the time of spring, and also for the 

 bursting open of the bark to allow for the growth 

 and increase of the wood." 



The remainder of the chapter is taken up with 

 remarks on the value of .various kinds of oak 

 timber deduced from his microscopical observations, 

 all of which tend to show that he made his micro- 

 scopes subservient to the particular study he was 

 then engaged in. 



His observations on the oak are succeeded by a 

 discourse on the microscopic structure of fir : " The 

 different Degrees of Goodness in Fir Timber ; how 

 discoverable; the minute Vessels which enter into 

 the Composition of this Tree described at large." 

 It is unnecessary to give any extracts from this 

 article, as it is similar to those already given. He 

 gives a very good figure of the dotted ducts which 

 be discovered. Tne minuteness of these vessels 

 astonishes him, and he scarcely expects to be be- 

 lieved by those who have not seen them. He con- 

 cludes by observing, " These discoveries of mine 

 respecting the smallness or thinness of the vessels 

 or tubes composing the substance of trees may not 

 easily be credited by many, as not comprehending 

 how, by reason of their exceeding smallness, any 

 juice or iiquor can possibly pass through them, and 

 what is more difficult to conceive, how, through such 

 vessels ascending perpendicularly, any nutritive sub- 

 stances can be derived from the root of the tree to 

 the extremities of the upper branches. 



" But as, on the one hand, it is out of the reach 



of our finite capacities to comprehend the extent of 

 the Universe, so, on the other, we are equally 

 unable to conceive the minuteness of the vessels 

 and component parts of which not only animals but 

 also vegetables are formed ; and much less how the 

 parts of matter are united together, or how one 

 part grows out of or is added to another." 



Leeuwenhoek was opposed to the theory of 

 equivocal or spontaneous generation, as explaining 

 the sudden appearance of living organisms where, 

 apparently, they had not previously existed. The 

 heterogenists have been driven from one stronghold 

 to another, until they have only the Bacteria to fall 

 back upon. 



Fig:. 11. Leeuwenhoek's figure of the Beak or Trunk of a Weevil. 

 "L, M. R is part of the head; N, the proboscis (which is not 

 so straight as here pictured, but appears bent down when 

 seen sideways) ; O, the month, showing: pincers or teeth. 

 Within this mouth are two piercers or stings, one of which 

 is seen in the figure. S, T are the two horns." 



Leeuwenhoek, in his chapter on the Weevil, or 

 corn-beetle, says : " I have heard it strongly argued 

 that the weevil, or corn-beetle (which is a very 

 noxious insect, well known to the corndealers and 

 bakers in this country), is produced by what is 

 called equivocal or spontaneous generation, that is 

 to say, from inanimate substances without any 

 parent. The principal reasons alleged in support of 

 this opinion are, that we often find this insect in a 

 new granary where never wheat was kept before, 

 and therefore it is deemed a necessary conclusion 

 that such weevils are not propagated by the ordi- 

 nary course of generation. Again, it is said that 

 we may open many grains of wheat which are 

 sound and uninjured, so that no mark of a perfo- 

 ration or hole shall be discernible on the outside, 

 yet within these grains shall be found perfectly 

 formed and living weevils." 



To this Leeuwenhoek replies that, although the 

 granary might be new and free from the insect, yet 

 the men who removed the corn, or the ship, waggon, 

 or cart, employed to carry the corn might be in- 

 fected with weevils by having carried grain on 

 which they abound, and thus, from a few of those 

 insects multitudes may be produced by the ordinary 

 course of generation. 



In order to demonstrate the truth of this, he 



