Revieios and Notices of Books. 131 



Manual of the Metalloids. Bj James Apjohn, M.D. , F.K.S. , 

 M.E-.I.A., Professor of Chemistry in the University of 

 Dublin. London : Longman & Co. 1864. 12mo. Pp. 

 596. 



In his preface the author states that the work has been written 

 as one of Galbraith and Haugh ton's series of Manuals on different 

 branches of science. The object has been to produce a condensed, 

 but at the same time tolerably comprehensive treatise, in which 

 no topic of importance should be omitted, while all would be dis- 

 cussed with as much brevity as is consistent with clearness. It 

 is intended as a handbook in Chemistry for students in medicine 

 and engineering. 



In the Introduction, the law^s of Combination, Chemical Notation 

 and Nomenclature, the Relations of Atomic Weights, the Law of 

 Volume, Atomic Volume, the Unitary System of Atomic Weights, 

 Isomerism, Chemical Formulae, Isomorphism, Dimorphism, Re- 

 action of Bodies on each other, the causes wdiich determine Decom- 

 positions, and the Division of Simple Bodies are considered. The 

 following are the fifteen substances which he considers as metal- 

 loids : — Oxygen, Hydrogen, Nitrogen, Sulphur, Selenium, Tel- 

 lurium, Chlorine, Bromine, Iodine, Fluorine, Phosphorus, Arsenic, 

 Boron, Silicon, and Carbon. The use of the simpler forms of 

 algebraic calculation has enabled the author to give precision and 

 brevity to many of his statements. At the present day, it is 

 clear that any one who wishes to study chemistry, must be pro- 

 perly instructed in arithmetic and the elements of algebra. 



In speaking of coal gas, Dr Apjohn remarks : — 



" Coal Gas. — A mixture of inflammable gases, to be burned for 

 the light, and sometimes for the heat it yields, has been derived 

 from different sources, viz., from turf, vegetable and animal oils, 

 and from rosin. The gas from turf has a low illuminating power, 

 and is now seldom made ; and that yielded by rosin and the oils, 

 though of good quality, is relatively so costly, that its manufac- 

 ture has also been abandoned. Our streets and houses are now 

 illumined exclusively by gas derived from bituminous coal; and 

 the subject, therefore, of the gaseous hydrocarbons cannot be con- 

 sidered as sufficiently discussed without some remarks upon the 

 preparation, composition, properties, and uses of this most im- 

 portant combustible substance. As an introduction to this subject, 

 attention is directed to the following table, which gives the ultimate 

 composition in 100 parts of a Welsh anthracite, of five specimens 

 of English bituminous coal, and of a variety of brown coal, or 



