;22 



NA TV RE 



[March 31, 1898 



If, however, instead of water they are kept over alcohol diluted 

 with an equal volume of water, they may remain wet for weeks, 

 without any such growth of mould or such alteration in the gum 

 as is produced by the action of stronger alcohol. It is very 

 desirable not to finally dry too quickly, but, as it were, to 

 anneal the specimens ; since contraction may give rise to 

 sufficient tension to cause them to crack and scale off from the 

 glass. 



I must now consider cases in which it is desirable to get rid 

 of part of the colouring-matter, either natural or developed on 

 keeping. Diluted sulphurous acid is very useful for this pur- 

 pose, and remarkable results can be obtained with small fishes. 

 If plaice about 2\ inches long are kept in alcohol and then for 

 a few weeks in diluted sulphurous acid, the earthy matter of 

 the bones is dissolved out and only cartilage left ; the general 

 colour is reduced, and the thickness diminished ; but strange 

 to say, the arteries and enclosed blood are so little altered that 

 when the specimens are mounted the aorta and branching 

 arteries are well seen over the whole animal, as shown in Fig. 

 4, which, however, fails to show the more minute arteries, quite 

 visible in the original. 



Having duly prepared the dried animals, it may not be 

 convenient to mount them at once in Canada balsam, especially 

 when living on a yacht. They may then be kept in tin boxes 

 with flannel which has been well dried at a fire, so as to absorb 

 any moisture that may be in the air. When thus kept, even for 

 many months, they usually do not undergo any sensible changes 

 and do not go mouldy. 



Fig. 4. — Plaice treated with sulphurous acid. 



I must now conclude by describing the methods employed 

 when finally mounting the specimens in Canada balsam. At 

 the four corners of the glass should be gummed small pieces of 

 blackened cardboard, of such a thickness that the cover-glass 

 will just clear the object and not rock. The glass with the 

 animal should be kept for a short or longer time in benzole ; 

 and, in the meanwhile, the cover-glass should be warmed on a 

 suitable stand over a small burner, and a fair quantity of liquid 

 balsam placed in the centre. The glass with the animal is then 

 taken out of the benzole, and carefully placed over the balsam, 

 so as to catch up as few bubbles as possible, the benzole causing 

 the greater part to burst and disappear. If too little balsam has 

 been used, more is easily run in between the glasses ; and if 

 only a few bubbles have been caught up, they soon disappear. 

 If there are more than desirable, they can be got rid of by 

 keeping the slide slightly inclined until they rise to one edge 

 and can be removed. After keeping cold for a few days, for 

 the balsam to harden the edges, it should be bound round with 

 thin paper of the best quality, made thoroughly wet with gum. 

 When this dries, contraction may squeeze out some superfluous 

 balsam. This paper should then be varnished, and finally strips 

 of good black paper should be glued well round the whole. All 

 possible care should be used to enclose the balsam thoroughly, 

 so as to avoid its turning yellow, and to prevent leakage, when 

 the slide becomes warm in the lantern. 



I have, however, had scarcely any trouble from this cause, 

 since I have so completely fastened it in that the glasses or 

 binding yield sufficiently. I may also say that though many of 



NO. 1483. VOL. 57] 



my slides have now been made for more than seven years, I 

 have not observed any deterioration, but, on the contrary, many 

 have greatly improved owing to the balsam having more com- 

 pletely penetrated into the tissues, and the included air dis- 

 appeared. When this has taken place, the specimens are far 

 rnore transparent and show their structure far better than the 

 living or dead animals. Nearly all my slides have been kept in 

 the dark, but some have been kept about the same time in 

 a strong light at the Sheffield Public Museum, Weston Park, 

 and, as far as can be judged, have not faded, even when 

 imjierfectly mounted. H. C. SORBY. 



OUR MINERAL WEALTH. 



TT would be difficult to conceive of a more concise and clearly 

 expounded compilation of statistics and general information 

 regarding mines and mining than that presented in the Third 

 Annual Report upon the Mineral Industry of the United King- 

 dom of Great Britain and Ireland, which has been issued by 

 the Home Office in the form of a Blue Book for the year 1896. 

 The volume before us is a synoptical review of the condition of 

 our own mineral indu.stry, as well as that of other countries, 

 which reflects unbounded credit upon its author, Dr. Le Neve 

 Foster, and those who have assisted him in the work. It is 

 divided into six parts, under the respective titles of persons 

 employed, output, accidents, prosecutions, general remarks, 

 and mineral statistics of the Colonies and foreign countries. It 

 contains, in addition, nineteen appendices, and concludes with 

 an exhaustive index. 



The statistics for the United Kingdom distinguish between 

 mines or underground workings and quarries or open workings ; 

 and the same figures are marshalled again and again under 

 different aspects, so as to show their varying significance when 

 coalfield is compared with coalfield, inspection district with 

 inspection district, and county with county. 



The first four parts include sixty-nine tables, in which the 

 various classes of information susceptible of being so dealt 

 with are compared with each other and with the correspond- 

 ing figures for the year 1895. These are followed by six 

 diagrams, on which are shown by means of curves, extending 

 from 1851 to 1896 inclusive, the yearly variations in the numbers 

 of persons employed above and below ground ; the output and 

 export of coal ; output, export, and import of iron ore ; deaths 

 due to accidents generally ; deaths from accidents, arranged in 

 five distinct classes (explosions, falls of ground, in shafts, mis- 

 cellaneous, and on surface) ; and the average quinquennial 

 death-rate per 1000 persons employed, classified in the same 

 way as in the last case. In Part iii. short descriptions are 

 given of the circumstances under which the most important 

 accidents of the- year occurred ; and throughout the volume 

 many pertinent remarks are made, which serve to throw light 

 upon the construction and meaning of the tables, point to the 

 conclusions which they justify, and infer the lessons that are to 

 be learnt from their perusal. 



Turning now to a consideration of the subject-matter, we find 

 that, taken altogether, there were 725,803 persons employed in 

 or about mines during the year under review — 576,325 working 

 in the mines, and 194,478, including 51 14 females, working on 

 the surface. Of these numbers 678,690 were employed at 3260 

 coal mines, 16,819 at 136 iron mines, and 30,294 at 720 other 

 mines. In addition to this there were 112,829 persons 

 employed at 7758 quarries. 



The quantity and value of the principal classes of minerals 

 mined and quarried were as follows : — 



