INTRODUCTION TO LETTER 18 113 
rough draft to be copied out in a fair hand before sending it to 
the Society. The letter is dated from ‘ Delft in Holland, 9th 
October, 1676”’ [New Style], and is addressed to Henry 
Oldenburg in person. From an endorsement which it bears’ 
it appears that he received it 10 days later, and sent back an 
acknowledgement of its receipt through Leibniz. The letter 
was read at the meetings of the Royal Society held on 1, 16, 
and 22 February 1677 [O.S. ].’ 
A part of this letter was published (in English) in the 
Philosophical Transactions in March, 1677,’ under the heading 
“ Observations, communicated to the Publisher * by Mr. Antony 
van Leewenhoeck, in a Dutch Letter of the 9th of Octob. 1676. 
here English’d: Concerning little Animals by him observed in 
Rain- Well- Sea- and Snow-water; as also in water wherein 
Pepper had lain infused”. (See Plate XVIII.) This English 
version was the work of Oldenburg himself, as is evident from 
the manuscript translation—in his hand—still preserved with 
its Dutch original. 
Oldenburg’s English rendering is the only version of 
Letter 18 which has hitherto been printed. It is, on the 
whole, good: but it is not perfect, and most people will be 
surprised to learn that it is a condensed translation of less 
than half of the original, and that the part which Oldenburg 
did not print has never yet been published in any language. 
Why the letter has never been published, in its entirety, I do 
not know. I can only suppose that no protozoologist or 
bacteriologist has ever yet seen the original manuscript; or, 
having seen it, has had the courage and diligence to decipher 
1 The endorsement—in Oldenburg’s hand—is as follows: “recew le 9. 
Octob. st. v. [=style vieux] 1676. resp[ondu]. le 16 Oct. d’avoir receu 
cette lettre, par M. Leibnitz, mais non pas encor consideré”’.—It was in the 
autumn of 1676 that Leibniz paid his now well-known (but formerly hushed- 
up) visit to Spinoza at The Hague (cf. Pollock, 1899; p. 37). Perhaps 
Oldenburg, knowing this interview to be imminent, requested Leibniz to send 
word to L.—only a few miles distant at Delft—of the safe receipt of his 
letter. I can find no evidence to show that Leibniz visited Leeuwenhoek 
on this occasion.—The well-known correspondence between L. and Leibniz 
took place, of course, at a much later date, and has been already reviewed 
by Ehrenberg (1845). 
2 Cf. Birch, Vol. III, pp. 332, 333, 334. 
* Phil. Trans. (1677), Vol. XII, No. 133, pp. 821-831. 
* “Publisher”? = Editor (¢.e. Oldenburg). 
8 
