94 PROGRESS OF MICROSCOPICAL SCIENCE. 



corpuscles do not dissolve in ether, but tliey dissolve almost entirely 

 in a large quantity of saline solution (one part of concentrated saline 

 solution in two parts of water). All these are properties which 

 belong to i^araglobulin. In blood preparations, therefore, which are 

 kept in a moist chamber, that is, in which, on the one hand, the 

 plasma becomes gradually diluted by absorption of water, and in 

 which, on the other hand, as it must be supposed, carbonic acid is 

 developed by decomposition, all the conditions are present under 

 which paraglobuliu may be precipitated. That Lostorfer's corj)Uscles 

 are to be met with abundantly generally only in blood preparations 

 from syphilitic patients, seems to show that theii- blood contains either 

 more jiaraglobulin or less fibrinogeous substance than other blood. 



Microscopic Appearances of Silica in the Galway Granites. — In an 

 able paper " On the General Microscopic Structure of the Irish Gra- 

 nites," which he read before the Eoyal Geological Society of Ireland 

 at a late meeting. Professor Hull, F.E.S., gave the following account 

 of the appearance of the silica in rocks. He says it occurs without 

 crystalline form enveloping all the other minerals. It is structure- 

 less, but full of cells, which are visible with a high power. With 

 polarized light, and on rotating the ui)per prism, the silica presents 

 the usual gorgeous play of colours, being broken up into distinct 

 patches of irregular form, each refracting different prismatic colours. 

 Some of the patches show round their edges parallel wavy bands of 

 prismatic colours, marking out the individuality of the patches, and 

 indicating the manner in which the particles consolidated in indepen- 

 dent masses of various sizes — sometimes exceedingly small. These 

 cells are often so minute that three successive series are brought into 

 the field upon changing the focus of the microscope by means of tho 

 mill-headed screw, with a magnifying power of 350 diameters. Along 

 with the cells are numerous long " belonites " or " trichites," some- 

 times perfectly straight, and stretching in all directions through the 

 mass of the silica. With the 1-inch object-glass these can be gene- 

 rally observed ; but with the ^-inch and the No. 2 eye-piece, magni- 

 fying 350 diameters, they are very well brought out, sometimes in 

 extraordinary numbers. Even with this power their apparent thick- 

 ness is not so great as that of the finest needle, with an apparent 

 length from an inch downwards. In one or two instances they appear 

 to be barbed, but this may be owing to the meeting of two trichites at 

 a point : there are also examples of trichites slightly bent or curved. 

 Sometimes the silica contains cells only without trichites. What the 

 nature of these needle-like objects may be I have no means of judging 

 from this slice. Cavities are exceedingly numerous in the silica. 

 Some of these resemble the forms described and figured by Mr. Sorby 

 in his admirable and well-known paper " On the Microscopical Struc- 

 ture of Crystals." They are of various shapes, enclosing the little 

 globule of fluid which just comes into view with a magnifying power 

 of 350 diameters, and must be less than yoViy ^^ ^^ ^^^h in diameter. 

 Others, however, are much larger, and sometimes do not appear to 

 contain any bubble ; and, as Mr. Sorby suggests, the fluid may have 

 escaped. Stone cavities, or appearances which I take to be such, as 



