ON THE INSTRUMENTS FROM LEYDEN. 185 



most in the field of science was an usher to the sage magistrates of a 

 little town in Holland called Delft. His name was Van Leuwenhoek, 

 a name which is now known throughout the whole world. Last year 

 we had not only a festival in Holland, but also in different parts of 

 Europe, to commemorate one of Van Leuwenhoek's greatest discoveries 

 of which I am to speak, and all these discoveries were made with the 

 little instrument I am showing you, of which every part was made 

 by himself. It consists only of a little lens, which is not as large as 

 the head of an ordinary pin, and the objects which had to be observed 

 were placed on a pin underneath. When we remember how well and 

 carefully arranged are the microscopes which we use now, we cannot 

 too much wonder how it was possible to make with such an apparatus 

 the discoveries which he made. The most important discovery was 

 that of the Infusoria those little microscopical animals which are to 

 be found nearly everywhere, and which give so much trouble to 

 modern science. In order to observe those infusoria he was obliged 

 to change the form of his apparatus a little, and constructed a micro- 

 scope of this form. His whole life was devoted to microscopical 

 researches, and you will understand this when I tell you that at 

 his death 247 microscopes with their frames were found, and also 

 172 lenses without frames. As often happens, his merits were 

 much sooner acknowledged by foreigners than in his own country, 

 and I am happy to say that it was Englishmen who were the first 

 to declare how great a man he was. He was made a Fellow of 

 the Royal Society, and that was, as he often declared, the greatest 

 blessing he ever received. I will now speak of another scientific man, 

 who lived quite another life namely, Christian Huygens, who was not 

 a man of humble extraction, for his grandfather had been Secretary 

 to the first Prince of Orange, and his father held the same office 

 under the following stadtholders, even under William the Third, who 

 was as much yours as ours. He at once saw that if astronomers were 

 to make greater discoveries it was necessary to have lenses of greater 

 focal length, and as these lenses could not be found in any part of 

 Europe, he, with his brother Constantine, made them himself. After 

 some trials he succeeded very well, and two or three days after his 

 first lens had been made, he was fortunate enough to discover a 

 satellite of Saturn, and afterwards he was able to solve a problem 



