A WEEKLY ILLUSTRATED JOURNAL OF SCIENCE. 



" To the solid ground 

 Of Nature trusts the mind which builds for aye" — Wordsworth. 



THURSDAY, MAY i, 1890. 



I 



THE APPLICATION OF THE MICROSCOPE 

 TO PHYSICAL AND CHEMICAL INVESTI- 

 GATIONS. 



Molekularphy sik , mil besonderer Beriicksichtigung mikro- 

 skopischer Untersuchungen und Anleitung zu Solchen, 

 sowie einen Anhang iiber mikroche7nische Analyse. 

 Von Dr. O. Lehmann, Professor der Electrotechnik am 

 kgl. Polytechnikum zu Dresden. 2 Volumes, pp. 852, 

 697, with 624 Woodcuts and 10 Plates. (Leipzig : W. 

 Engelmann, 1888-89.) 



VERY soon after the first invention of the microscope, 

 attempts were made to apply the new instrument 

 to solve some of the remarkable problems of crystallo- 

 genesis. The early volumes of the Royal Society Trans- 

 actions contain in the papers of Boyle, Hooke, and Leeu- 

 wenhoek,published between the years 1663 and I709,many 

 records of attempts of this kind ; and the works of Henry 

 Baker, which appeared between 1744 and 1764, are also 

 largely concerned with the study of the process of crystal- 

 lization under the microscope. 



In Germany, Ledermuller in 1764 and Gerhardt in 1780 

 showed the value of the microscope in studying the in- 

 ternal structure of crystals ; while in France a long 

 succession of enthusiastic investigators, Daubenton, 

 Dolomien, Fleurian de Bellevue, Cordier, and others, were 

 busily engaged in laying the foundations of the science of 

 microscopical petrography. 



Early in the present century, we find the English 

 investigators once more taking a leading part in apply- 

 ing the microscope to the study of crystallized bodies. 

 Between the years 1806 and 1862, Brewster published a 

 long series of memoirs, dealing with the microscopical 

 characters of natural and artificial crystals, and the in- 

 clusions which they contain. About the year 1850,100, 

 Mr. Sorby commenced his important investigations on 

 the subject, availing himself of the method of preparing 

 transparent sections of rocks and minerals which had 

 been, shortly before this time, devised by William Nicol. 

 Mr. Sorby's epoch-making memoir " On the Microscopical 

 Vol. xlii. — No. 1070. 



Structure of Crystals, indicating the Structure of Minerals 

 and Rocks" made its appearance in 1858. 



While one group of investigators, following the lines of 

 the early work of Brewster and Sorby, have sought to 

 make the microscope an efficient instrument for the de- 

 termination of minerals, even when present in rocks as 

 the minutest crystals or fragments ; others have no less 

 diligently pursued the methods which the same pioneers 

 in this branch of research have initiated for solving 

 physical and chemical problems connected with the for- 

 nvation of crystallized bodies. 



In the hands of Des Cloizeaux, Tschermak, Zirkel, 

 Von Lasaulx, Fouqud and Michel-Ldvy, Rosenbusch, and 

 other workers, the microscope has gradually been de- 

 veloped into a splendid instrument of mineralogical 

 research ; and the determination of the minutest particles 

 of a mineral is now becoming no less easy and certain 

 than that of the largest hand-specimens. 



But, at the same time, Brewster and Sorby's early 

 attempts to solve physical and chemical problems by the 

 aid of the microscope have not failed to exercise an 

 important influence on subsequent workers in these 

 branches of science. Link, Frankenheim, Klocke, Hart- 

 ing, and especially Vogelsang (whose early death was a 

 very severe loss to this branch of science), have done 

 much towards establishing the science of crystallogenesis 

 upon a firm basis of accurate observation ; and their 

 labours have been continued in more recent times by H. 

 Behrens and Dr. Otto Lehmann, the author of the work 

 before us. 



As the well-known treatises of Rosenbusch, and of 

 Fouqud, Michel-L^vy, and Lacroix, give us an admirable 

 rA«w/ of the present state of determinative mineralogy, 

 as improved by the application of the microscope, so 

 does the work before us contain a perfect summary of 

 the contributions of the microscopist to the sciences of 

 physics and chemistry. 



It will only be possible, within the limits of an article 

 like the present, to indicate briefly the plan of the very 

 comprehensive, and, indeed, almost exhaustive work, in 

 which Dr. Lehmann has embodied the observations of 

 himself and his predecessors in this field of inquiry. 



The first division of the book deals with the construe- 



