10 INTRODUCTORY ADDRESS: 



that it is not meant to indicate that knowledge has not been accumu- 

 lated and that, for example, we shall in the future be dependent 

 upon foreign supplies as in the past ; it is hoped quite the contrary. 

 It is one of the main objects of this Symposium to bring forth and 

 prove that all these requirements can and will be met by the Anglo- 

 Saxon, or at any rate that this will be possible in the immediate future. 



It should be added that there stands out very prominently in 

 this connection the important work done on behalf of Glass Tech- 

 nology by Sir Herbert Jackson, K.B.E., to whom we are greatly 

 indebted, and who will give us an important Address this evening. 



Reference should also be made to the excellent work carried out on 

 this subject by the National Physical Laboratory, where systematic 

 work on the attack of various refractory bodies by molten glass under 

 carefully standardised conditions has been continued, together with 

 work on the production of crucibles increasingly resistant to such 

 attack. Progress has been made in the application of fused zirconia 

 as a lining for crucibles. In the course of this work special phenomena 

 have been observed in the attack which occurs in some cases at the 

 bottom of the crucible, and in others, at the level of the surface of the 

 glass. These phenomena have been studied by means of experiments 

 on the mode of solution of such substance as wax, naphthaline and 

 plaster-of-paris in ordinary solvents at room temperature where the phe- 

 nomena could be observed. Most of the features met with in the attack 

 of molten glass on crucibles have been reproduced in such experiments, 

 and a method of preventing the worst features of such attack has been 

 tried and found successful in the model experiments. In addition 

 reference should be made to the valuable work done by the Society 

 of Glass Technology at the University of Sheffield, in which Dr. W. E. S. 

 Turner, the honorary secretary, has played so important a part. 



It is certainly most necessary that we should not be behind 

 but abreast of our Foreign competitors in the making of Microscopes 

 and Lenses or their use. One of the prominent objects in holding the 

 Symposium is to arouse still more interest in the advancement of this 

 work. 



SECTION II.— HISTORY OF THE MICROSCOPE. 



Ancient Times to 1600 a.d. 



If the Microscope is considered as an Instrument consisting of one 

 Lens only, it is not at all improbable that it was known to the Ancients, 

 and even to the Greeks and Romans. The minuteness of some of the 

 pieces of workmanship of the Ancients would appear to indicate that 

 they must have been executed by the use of Magnifying Glasses. 

 Many passages in the Works of Pliny, Plutarch, Seneca, and others 

 clearly indicate this. 



There is reason to believe that the magnifying power of transparent 

 media with convex surfaces was known very early. The convex Lens 

 of rock crystal was found by Layard among the ruins of the Palace of 

 Nimrod. Seneca describes hollow spheres of glass filled with water 

 as being mainly used as magnifiers. It is practically certain that 



