1 88 SECTION PHYSICS. 



the right." He was as joyous, his relative relates, as if he had just dis- 

 covered that he was in the right. It was by that experiment that the 

 matter was settled for ever. You will also find downstairs a very in- 

 genious apparatus invented by ; sGravesande, by which he has been 

 able to prove by experiments that the same quantity of labour pro- 

 duces always the same quantity of vis viva. I should certainly have 

 some more things to add, but I have already spoken, I fear, too long. 

 The CHAIRMAN : I do not think that Dr. Rijke need have made 

 any apology for his want of fluency in speaking English, for he has 

 given a most lucid description of these wonderful contributions to 

 science of his countrymen. The compound microscope of the Janssens, 

 but more remarkable still, the simple microscope of Leuwenhoek, 

 whose name every microscopist is well acquainted with, certainly 

 performed wonders. These simple lenses showed an amount of 

 detail in the objects he examined which for a long time was unre- 

 vealed, and certainly was not revealed for a long time by the com- 

 pound microscope. Of course it is not to be compared with the 

 microscopes of the present day, but in its day it was a remarkable 

 instrument. Dr. Rijke has also alluded to the two Huygens, and 

 these lenses upon which I place my hand belong to the Royal 

 Society, and as you are aware they were mounted with a ball and 

 socket and a balance, and placed at the top of a high pole. The 

 eyepiece was held in the hand, and the object glass was controlled 

 by a long rod and a string. The observer had first to find his object 

 glass with a lantern, and when he found it, turn it on to a star and 

 seize the blaze of light in the object glass, and then he went on 

 observing. In the lower room is a tower constructed on piles, which 

 was intended by the Royal Society for mounting, at the suggestion of 

 Mr. Struve, the celebrated Russian astronomer, these object glasses 

 of Hugyens, with a view of ascertaining whether there was any change 

 in Saturn's rings. A theory had been started that the rings were 

 altering and collapsing. It was found to be rather expensive, and 

 Mr. Struve on reconsideration did not press for the expenditure of 

 400/. or 5007. for mounting them. I have myself looked through these 

 object glasses and can attest that they are very good ones. I did not 

 look at a celestial object, but at a test object on the Pagoda at Kew. 

 Now I believe Mr. Lockyer has employed them with a siderostat for 



