ZOOLOaY AND BOTANY, MICROSCOPY, ETC. 181 



of a mass of fine, elongated fibres, which are matted and interlaced in 

 a manner which very much resembles hair. In gold, this fibrous 

 structure, although present, is far less marked. The influence of 

 extreme pressure upon gold and silver seems to be, therefore, to 

 develope a definite internal structure. Gold and silver, in fact, appear 

 to behave in some respects like plastic bodies. When forced to 

 spread out in the direction of least resistance their molecules do not 

 move uniformly, but neighbouring molecules, having different velo- 

 cities, glide over one another, causing a pronounced arrangement of 

 particles in straight lines. 



This development of a fibrous structure, by means of pressure, in 

 a homogeneous substance like silver, is an interesting lesson in expe- 

 rimental geology, which may serve to illustrate the probable origin 

 of the fibrous structure of the comparatively homogeneous limestones 

 of the Pyrenees, Scotland, and the Tyrol. 



Sections of Fossil Coniferous Woods. — Voigt and Hochgesang of 

 Gottingen have issued (price 65 marks) a collection of seventy micro- 

 scopi-c slides of coniferous woods, fossil and recent, prepared by 

 Professor Goppert. The present collection is a first instalment only, 

 and is devoted to the Araucarieae. Where possible, each species is 

 represented by three sections, one transverse, the second central or 

 radial, and the third cortical or tangential. Sections of recent woods 

 are placed side by side with those of the most nearly allied fossil 

 woods ; as sections of an Araucaria (A. CunningJiami) and of a 

 Dammara (D. australis) by the side of the fossil Araucarites. The 

 preparations are arranged in a polished mahogany box with ledges, 

 and have been made on slides of white glass 50 x 33 mm., and 

 1 ' 5 mm. thick, with polished edges, under square cover-glasses of 

 18 mm. length and breadth, in Canada balsam. Only those of the 

 recent Araucarieae are under round cover-glasses of 20 mm. diam. in 

 glycerine. The sections have been made with the greatest care and 

 skill. Instead of the ordinary length of about 4 mm., these are 

 of double or treble that length, so as to render possible a more com- 

 plete examination. Special care has been taken to furnish sections 

 which illustrate the nature of the process of petrifaction. 



Aeration of Laboratory Marine Aquaria.* — The plan shown in 

 Fig. 27 is recommended by M. Kunckel d'Herculais for aerating 

 a salt-water aquarium by means of a fall of fresh water. 



The figure shows two aquaria, A being fresh-water and B salt- 

 water. In the first case the process is of course very simple, the 

 water from the pipe C passing down the tube E, air being obtained 

 through the tube F and pipe D which communicates with the open 

 air so as to prevent air being abstracted from the confined laboratory. 



In the case of the salt-water aquarium B, the fresh-water passes 

 from the pipe C down the tube G into the bottle H, with three 

 openings, which holds about two litres, air being obtained as before 

 from the open air through D and the tube shown on the right. A 



* See 'Manuel de Zootomie,' par A, Mojsisovics, traduit par J. L. de Lanessan 

 (8vo, Paris, 1881), pp. 61-6 (1 fig.). 



K 2 



