82 Notices of Scientific Works. [Jan., 



diamond is said to weigh about 53 carats, and being only rose-cut, 

 one carat may be valued at 15?. Then, according to our rule, the 

 value of the diamond may be thus expressed in pounds : 

 *-£ (53 + 2) 15 = 26-5 x 55 x 15 = 21 ,862 '5. 



It must be admitted that this is a tolerably near approximation 

 to the true value, when it is stated that the diamond was sold by 

 Prince Demidoff to Sir Jamsetjee Jejeebhoy for 20.0007. 



Perhaps the most useful part of this work is to be found in the 

 concluding chapters, which explain the method of determining an 

 unknown gem, the results of which are afterwards collected in a 

 tabular form. 



"We shall be glad to see so excellent a work as this translated 

 into English. 



SENFT'S MINERALOGY AND LITHOLOGY.* 



If one branch of natural science, more than another, deserves to 

 find a place in any improved scheme of scholastic education, that 

 science, according to Dr. Senft, is undoubtedly Mineralogy. For, 

 apart from its practical value to all whose daily occupation brings 

 them into contact, directly or indirectly, with the products of the 

 mineral kingdom — such as the miner, the builder, the agriculturist, 

 and the manufacturing chemist — the study of mineralogy is so 

 closely connected with that of many collateral sciences that a course 

 of mineralogical lectures, properly delivered, might be made the 

 means of imparting to a class much valuable information on the 

 sciences of chemistry, physics, and geology, to say nothing of solid 

 geometry. Hitherto this relation of mineralogy to other branches 

 of science has been regarded as a great stumbling-block to the 

 student, inasmuch as he must needs acquire a rather wide range of 

 knowledge before he can successfully cope with the difficulties of 

 mineralogy. These difficulties may, however, be removed, to a 

 great extent, by an attractive style of instruction, adapted to the 

 capacity of the pupil, but at the same time not superficial enough 

 to nullify the efficiency of mineralogical study as a means of intel- 

 lectual training. Five-and-twenty years' experience in teaching 

 science to youths between fourteen and sixteen years of age, has led 

 our author to mature a scheme of instruction which he regards as 

 best adapted to meet the wants of those who may not wish to push 

 then mineralogical studies beyond a very moderate acquaintance 

 with the more important species. He devotes to this study only 

 two hours weekly, but he extends the course over two years. The 



* Lehrbuch der Mineralien und Felsartenknnde. Von Dr. Ferdinand Senft 

 Svo. Jena, 1869. Pp. 656. 



