LEEUWENHOEK’S SEALS 359 
In addition to the information given in this table, I must 
note the following points: 
(1) Leeuwenhoek sent a complete copy of his Letter 4 
(1 June 1674, to Oldenburg) to Const. Huygens, and the MS. 
is preserved at Leyden. ‘This copy has recently been printed 
by Vandevelde and van Seters (1925). 
(2) Letter 19 (23 March 1677) and Letter 21 (5 Oct. 1677) 
are quoted extensively by Leeuwenhoek himself, in his own 
language, in his Letter 96 (9 Nov. 1695, to the Elector Palatine) 
printed in the Dutch works—with Latin versions, of course, 
in the corresponding Latin editions. 
(3) Letter 22 (Nov. 1677) is quoted, almost entire, in its 
original Dutch, by Leeuwenhoek in his Letter 113 (17 Dec. 
1698, to Harmen van Zoelen—published in the collective 
editions) : and a complete English translation of it (made but 
not published by myself) has now appeared in the recent 
work of Cole (1930). 
(4) Finally, I must note that the printed Catalogue of the 
Royal Society MSS., compiled many years ago by the youthful 
Halliwell-Phillipps (1840), is not free from errors; and 
accordingly its entries relating to the Leeuwenhoek MSS. are 
not to be accepted as invariably accurate. 
(viii) LEEKUWENHOEK’S SHALS 
Seals on old manuscripts are often important for purposes 
of identification: how important they may sometimes be, I 
know from the following incident. Recently, Carbone (1930) 
believed that he had discovered a new Leeuwenhoek letter 
among the Magliabecht MSS. in the National Library at 
Florence. This document was among the genuine letters of 
Leeuwenhoek addressed to the Florentine scholar, but was 
unsigned. Carbone reproduced it in facsimile—including the 
seal (enlarged). From its contents it was at once evident 
to me that this letter (written in Latin, and dated 2 May 1692 
from Hanover) could not possibly have been written by 
Leeuwenhoek. I guessed immediately, however, that it was 
written by Leibniz: and on comparing it with Leibniz’s 
extant letters to the Royal Society, I found that the cor- 
rections throughout were apparently made in his handwriting, 
and that the seal was one which he used. A seal is often 
as good as a signature (for no man lent his seal-ring to 
