338 LEEUWENHOEK AND HIS “LITTLE ANIMALS ”’ 
own “table of weights ” himself, so that we know their relative 
values. Writing to Tschirnhausen * in 1699 he says:° 
Over here we divide a pound |pont] into 16 ounces 
[oncen], and each ounce into 20 engels,* and each engels 
into 32 grains [asen]; and consequently, then, a grain 
[aas] is todz0 Of a pound. 
Tt is thus clear that Leeuwenhoek’s “grain” (aas), which 
was gto of his ounce, can hardly have been identical with our 
modern grain (4373 = 1 ounce, or 7,000 = 1 Ib. avoirdupois). 
Wherever I translate “asen” as “ grains”, in the foregoing 
pages, it is merely for want of any other term ; and the reader 
will therefore please bear in mind that Leeuwenhoek’s * grain ” 
was only approximately the weight nowadays called by the 
same name in English (1 grain=0°065 gramme). But these 
are problems for the expert metrologist—not for a poor 
protozoologist or bacteriologist—and their further discussion 
is beyond my competence. 
(iv) LEEUWENHOEK’S DWELLING 
The tragicomical history of Leeuwenhoek’s house in Delft 
has never yet been fully related, but it deserves notice here 
for several reasons. ‘These are the facts, so far as I have been 
able to ascertain them. My information is derived chiefly 
from Soutendam (1875), Haaxman (1875), Harting (1876), 
Bouricius (1924, 1925), and an anonymous article” recently 
published in the Wereldkroniek—supplemented by a few 
personal observations and inquiries made on the spot in 1923. 
In September 1875 an international celebration of “the 
200th Anniversary” of Leeuwenhoek’s discovery of the 
“Infusoria’”’ was held at Delft. (Harting [1876] records the 
events which led up to this congress.) The fixing of the date 
of the original discovery on September 1675 was, as we now 
1. W. von Tschirnhausen (1651-1708), the well-known German 
mathematician. 
2 Letter 120, dated“. . . 1699.” Published in Dutch and Latin 
collective works. See p.131 of Dutch edition. 
* There is no English equivalent of this word. 
4 See Anonymus (1909). 
