Reviews — J. Allen Howe — Kaolin, China-clay, etc. 373 



No remarks on this handbook would be complete without reference 

 to Appendix 1, from the pen of Mr. Allan B. Dick, which de/scribes 

 a novel way of examining mineral fragments under the microscope, in 

 especially selected media of requisite refractive indices, with dark 

 ground illumination. Only those who have had the advantage of 

 seeing the method in operation can fully appreciate its beauty and 

 the ease with which kaolinite crystals can be detected, and it is to be 

 hoped that the method will find considerable application in that very 

 difficult region of investigation, the microscopic examination of clays. 



In 1893 the handbook to the Collection of British Pottery and 

 Porcelain at Jermyn Street was issued and formed the first of the 

 series of handbooks that replaced mere catalogues. The valuable 

 notes on British Clays compiled by Mr. George Maw were included 

 in that volume, and a worthy successor to it has been found in the 

 handbook under review, which forms the second publication on clays 

 issued from the Museum of Practical Geology. Information with 

 regard to clays is scattered and often inaccessible, and it is to be 

 regretted that greater advantage is not taken of such publications 

 as those just mentioned. Textbooks on geology and chemistry give 

 almost nothing, and anyone wishing to get an insight into the 

 properties of clays could hardly be better advised than to read these 

 handbooks. The study of clays has not received the attention it 

 deserves, and the fact is often overlooked that the output of clays, 

 together with the closely allied material, shale, in this country is only 

 exceeded by two other mineral products, coal and iron-ores. Though 

 a large portion may be of relatively low value, still clay is the 

 essential constituent of products which range from an exquisite 

 work of art to a common building brick, and without refractory clays 

 hardly a single manufacture could exist. 



In conclusion, the author is to be congratulated on having attained 

 two dissimilar objects in one volume with marked success ; the general 

 visitor to the Museum is provided with an interesting handbook, and 

 the specialist with a valuable scientific textbook. Kaolin might 

 perhaps be described as the fundamental or parent clay, but owing to 

 the remarkably complete series of geological formations represented in 

 this country, we have many deposits of great economic value which 

 supply raw material for all branches of ceramic manufacture, such as 

 ball clays, stoneware clays, and fire-clays. Consequently it would 

 seem that the authorities at the Museum of Practical Geology would 

 be fulfilling the mandate received in 1835 "to form collections 

 illustrative of the mineral wealth of the country and of the 

 applications of its various mineral substances to the useful purposes of 

 life", if the present handbook were followed up by others, dealing 

 with the special and more important classes of clays such as those just 

 mentioned, and gigantic though the task might be it is not too much 

 to say that its execution could not be in better hands than those of 

 the present Curator. 



W. C. H. 



