MINERALOGY. 535 



nothing to be desired, and tliey will be of great assistance to those who 

 are either studying or teaching this branch of mineralogy. Thus far 

 four numbers of this work have appeared. 



This seems to be the proper place to mention the SJcetch of the Prog- 

 ress of American Mineralogy by Prof. G. J. Brush, delivered as the presi- 

 dential address before the Montreal meeting of the American Associa- 

 tion for the Advancement of Science, in August, 1882. This address 

 gives an interesting and valuable account of the development of the 

 science of mineralogy in America, commencing from its earliest begin- 

 ning with the formation of the "American Mineralogical Society," in 

 1708. The great ignorance of the science which characterized the early 

 years of this century is shown, and then the successive steps are pointed 

 out which have gradually led up to the advanced position of mineralogy 

 in this country at the i>resent time. As typical of the work done and 

 the workers engaged in it, sketches are given of four leading mineral- 

 ogists : Dr. Archibald Bruce, who founded the American Mineralogical 

 Journal ; Col. George Gibbs, whose collections made abroad afforded a 

 great stimulus to the development of the science at home ; Prof. Parker 

 Cleaveland, author of the most valuable work for the time, an Elemen- 

 tary Treatise on Mineralogy and Geology; and Prof. Benjamin Silliman, 

 of Yale College, who established the American Journal of Science. 



2. CRYSTALLOGRAPHY AND PHYSICAL MINERALOGY. 



Among the recent general treatises devoted to crystallography and 

 physical mineralogy, those of Tschermak and Bauerman have already been 

 alluded to. In addition to these the Geometrische Krystallograpliie by Lie- 

 bisch is to be mentioned. It devotes nearly 500 octavo pages to the devel- 

 opment of the subject, and accomplishes this with system and thorough- 

 ness. Eammelsberg has published the first volume (615 pp.) of a new 

 edition of his Handhuch der Icrystallographisch-physiJcalischen Chemie^ a 

 work which is a valuable auxiliary to the study of minerals, although 

 discussing the crystalline form of artificial compounds. The Stereogra- 

 pliisclie Projection of Eeusch will be a help to those studying the system 

 of mineralogy based upon it. 



A noteworthy advance in the methods of research in physical miner- 

 alogy has been made through the introduction of a solution of mer- 

 curic iodide in potassium iodide as a means of determining the specific 

 gravity of minerals, and also of separating different minerals when mixed 

 together in the form of small fragments. The solution, called the Son- 

 stadt solution, because proposed by E. Sonstadt in 1873, has a high 

 specific gravity, attaining at a maximum about 3.2, so that a fragment 

 of fluorite floats in it. This specific gravity can be varied almost in- 

 definitely by the gradual addition of water, so that it may be used to 

 determine the specific gravity of any mineral not heavier than the limit 

 mentioned ; all that is necessary being to obtain the weight of a known 

 volume of the liquid in which the mineral in question just floats. The 



