50 TRANSACTIONS AND rr.OCEEDIXGS OF THF^: [Sess. lxi. 



now supplies an 80 mm. objective containing an iris- 

 diaphragm on the principle of a photographic lens, which 

 suits admirably for this kind of work. 



The ocular is removed, and a tube of mat-black paper 

 substituted : the microscope so altered is clamped to the 

 base board, the tube bent over into the horizontal position, 

 and coupled on to the camera, and all the parts thrown 

 backwards so that their ends lie in one vertical plane and 

 allow the block to be brought as near the lens as may be 

 desired. 



Illumination, focusing, and exposure are the same as in 

 the first method, but greater care, if possible, is required. 



■ EEFERENCES. 

 Bousfield's Photomicrography. 



Carlier and Mann, Proc. Scot. Micro. Soc. 1893-94. 

 Forgan, do. 1894-96. 



Pi.ATE. 

 This is a reproduction of a pliotograph taken by Metliod I. of the 

 cross surface of a block of oak wood. The diagnostic points are well 

 brought out, viz. characteristic medullary rays, porous spring zone, 

 radial lines of pores in autumn wood, and tangential lines of parenchyma 

 in the autumn woo;l of broad rings. 



On the Histological Stiiuctuee of Fossil Woods. 

 Part I. (Abstract). By 11. A. Kobektson, M.A., B.Sc. 

 (Read 8th April 1807.) 



The history of specimen I. of this series, in the museum 

 of St. Andrews University, has been lost. The stem is 

 silicified, and somewhat weathered on the exterior, and 

 structurally is a very interesting one. One transverse face 

 has been polished, and measures about 5h inches by 3 

 inches. The stem has been distorted by pressure in the 

 radial direction, the effects of which are seen in the 

 collapsed vasa, narrowed rings, medullary rays, and wood 

 parenchyma. The pith shows no structure, being merely 

 an amorphous mass of silica. In outline, the section is 

 oblong, with one corner rounded off. On this rounded 

 side, measuring 3| inches by 1 inch, a few annual rings 

 are preserved intact, sliowing the diagnostic histological 

 character of the wood. 



