Dec, 2 2, 1887] 



NATURE 



171 



is not on record where these personages joined company 

 before they set out westwards for Jerusalem. 



As comets long afterwards were supposed to pre- 

 sage disaster, so the star may have been regarded as 

 an indication of the approaching death'of King Herod. 

 This would start the question as to his successor, whom 

 the " wise' men " ^ould desire to stand 'well with, or 

 to i" worship." With what happened at Jerusalem we 

 have nothing to do. On approaching Bethlehem about 

 noon, they again recognized the star over the town, as 

 Venus would be at that time, on the supposition that the 

 "star in the East" which they had first seen was really 

 that planet. 



Another point connected with this matter relates to the 

 question of new stars. Supposing there were a new star 

 in the east, why should the population be affrighted ? 

 The records of astronomy, as we have seen, tell of a con- 

 siderable number of such stars, and during the last few 

 years we have been favoured with our fair share of such 

 appearances, and yet the world is none the worse for 

 them. The view which has recently been put forward, 

 with an amount of evidence to back it which almost puts 

 it beyond question, is that in new stars we see only such 

 phenomena as we must expect ; we see the result of 

 no unnatural dealings with the regulated order of the 

 universe, but simply the collisions of swarms of meteorites, 

 these meteorites being not only not in our own system, 

 but lost, it may be, in the very depths of space. Why 

 should such a thing as this affright us? It is simply 

 what happens at a level crossing when a train runs into a 

 cart, and it does not seem likely that such an ordinary 

 piece of mechanism as this would be chosen as a means 

 of frightening or ringing the death-knell of a world. 



Modem science, while thus abolishing mystery from the 

 skies, is only enhancing the majesty of all created things. 

 The universal law and order are more clearly seen in 

 every great advance ; and yet, with a population so super- 

 stitious that the least uncomprehended thing affrights 

 them, our statesmen are still on the side of ignorance, 

 and hinder rather than aid the introduction of science 

 into our schools. 



THE MICROSCOPE. 



The Microscope in Theory and Practice. Translated 

 from the German of Prof. Carl Naegeli and Prof. S. 

 Schwendener. (London : Swan Sonnenschein and 

 Co., 1887.) 



I^HIS book opens to English readers an entirely new 

 page in microscopical literature. It leads the way 

 in supplyinga want which every thorough microscopist has 

 reaHzed for the last twenty years. In a complete form 

 this treatise has been accessible to the German reader 

 for at least ten years. The absence of it, or an equivalent, 

 in the English language has been a most serious draw- 

 back to the advancement of the highest optical work 

 in English microscopes. In optical manipulation, the 

 English optician at his best proves not only equal to any 

 in the world, but, in the highest class of work, has shown 

 lately that he takes a foremost place. But with no 

 attempt on the part of English mathematicians and 

 microscopists to become masters and expounders of the 

 theory of the microscope and of microscopic vision, the 



practical optician can make no real advance. English 

 " stands," and those made in America on English models, 

 are of exquisite construction, and are quite equal to our 

 present necessities ; but, for all the great advances and 

 improvements that have been made in English object- 

 glasses during the last fifteen years, we are, for all 

 practical purposes, primarily indebted to Germany. And 

 this is readily explained by the fact that the German 

 specialists have made a systematic and persistent study 

 of the theory of the microscope. 



It is not forgotten that it was to the suggestion of Mr. 

 J. W. Stephenson that we are indebted for the invaluable 

 improvements that belong to the homogeneous system of 

 lenses.^ But, without doubt, it was on account of the in- 

 sight which a study of the theory of microscopic vision 

 brought with it, that Mr. Stephenson perceived at once 

 the advantages of great numerical aperture, and the new 

 way to obtain it. Moreover, it is certain that Prof. Abbe 

 was approaching this very method of employing lenses, 

 though from another point, and not in so direct a way. It 

 would have been shortly reached by him there can be but 

 little question ; but when it was reached, what did a con- 

 stant, enthusiastic, and laborious study of the theory of 

 the microscope carry with it ? A perception, that with 

 glass of greater range of refractive and dispersive indices 

 than any we possessed, we might not only secure great 

 numerical apertures, but secure them devoid of all colour ; 

 that we could not only annul the primary, but also the 

 secondary and tertiary, spectra. It need not surprise us 

 then, that, in a country where such splendid theoretical 

 and mathematical work had been done by experts on the 

 principles of microscopic lenses and the laws of their 

 construction and use, even the Government should be 

 convinced that the time to aid the optical expert had 

 come ; that theory had demonstrated the practical possi- 

 bility of a great improvement in the construction of 

 lenses. The sum of ^6000 was granted by the German 

 Government to Abbe and his coUaborateurs, and with, 

 as we have reason to believe, an equivalent outlay on 

 Abbe's own part, the new glass was prepared ; and the 

 new Apochromatic lenses with their systems of com- 

 pensating eye-pieces devised. 



It is in no spirit of boast, but rather in a spirit of 

 humiliation and regret, that we say that we have examined 

 many of these apochromatic objectives of all the 

 powers made in Germany, and we have examined all the 

 principal ones that have, since the new glass has reached 

 London, been made there ; and we are bound to say that 

 the English work, based on the principles laid down 

 by Abbe, is so fine as to make the regret immeasurably 

 keener that English microscopical literature has been for 

 all these years a blank, for practical purposes, on the 

 theory and principles of optical construction, and on the 

 theory of microscopical observation and interpretation. 

 Such a paper as that of Prof. G. G. Stokes, P.R.S., 

 ' on the question of a theoretical limit to the apertures of 

 ! microscopic objectives (Journ. R.M.S.,vol. i. p. 139) ^ro"^ 

 its very loneliness only gives emphasis and point to our 

 contention. Those who have any doubt of the full force of 

 what we are here contending for, have only to compare a 

 dry J-inch objective, say of twenty-five years ago, made 



' "On a Large-angled Immersion Objective, without Adjustment Collar 

 with some Observations on Numerical Aperture," by J. W. Stephenson 

 F.R.A.S. (Journ. Roy. Micros. Soc. vol. i. p. 51). 



