NoVBurBEE 29, 1895.] 



SCIENCE. 



739 



mon mineral species, chiefly by means of their 

 physical properties with confirmatory chemical 

 tests. A special feature is the addition of a 

 supplemental table for the determination of one 

 hundred of the rarer minerals, thus avoiding 

 for the student the unnecessary use of a large 

 cumbersome scheme, and at the same time re- 

 ducing to a minimum the chances of meeting a 

 mineral not contained in the Tables. 



The general idea of the scheme is to make 

 two grand divisions into the minerals with and 

 the minerals without metallic lustre. The minerals 

 having metallic lustre being further sub-divided 

 into groups by their color and approximate 

 hardness. The minerals vi^ith non-metallic lustre 

 being grouped by color of streak, approximate 

 hardness, specific gravity and general structure. 



These Tables carry out the idea that a scheme 

 is the better, the more closely it tends to facili- 

 tate recognition of minerals at sight by their 

 structural and physical characters. For this 

 reason chemical tests are only used as confirma- 

 tory and are made as simple as possible, so as 

 to put them within the reach of persons having 

 only a blowpipe outfit. Schemes- of this char- 

 acter can be used with great success by students 

 who are more or less proficient in mineralogy, 

 and who have been carefully trained in observa- 

 tion. One part of the scheme that might give 

 trouble to beginners is the required determina- 

 tion of the specific gravity of the non-metallic 

 minerals. A determination for which special 

 apparatus is needed and which is generally 

 more or less difficult. Schemes for the non- 

 metallic minerals based on fusibility and solu- 

 bility, especially when dealing with massive 

 minerals, may give more general satisfaction 

 when used by beginners. 



The introductory part includes a detailed 

 description of the morphological, physical and 

 chemical properties of minerals, and a short 

 explanation of the blowpipe tests made use of 

 in the Tables. A simple and inexpensive form 

 of specific gravity apparatus is also described. 

 A list is furnished the student of fifty of the 

 common minerals, giving very characteristic 

 tests and most viseful in commencing a course 

 of determinative mineralogy. 



A very convenient chapter is that on ' How 

 to use the Tables.' Here the structural, physi- 



cal and chemical properties of several minerals 

 are given, and the student is taken, step by 

 step, by reference to page, etc., through the 

 actual determination or confirmation of the 

 mineral. A great advantage in this scheme is 

 having the general synopsis all contained on 

 one page, after reference to which it is generally 

 possible to turn immediately to the part of the 

 Tables needed for the determination of the 

 special mineral in question. 

 ■ The separation of the scale of hardness into 

 five divisions instead of ten also has its advan- 

 tages, as it makes possible the use of the Tables 

 when only an approximate determination of 

 the hardness has been made. 



After each mineral species in the Tables a 

 number, in parenthesis, is given, which refers to 

 the synopsis of classification where at a glance 

 the general relation of the special mineral to 

 the rest of the mineral kingdom is given. 



At the end of the Tables a very convenient 

 index of mineral names and synonyms is found. 

 Lea McI. Luqueb. 



Fauna fosil de la Sierra de Catorce, en San Luis 

 Potosi. Aguileea y Del Castillo. Bole- 

 tin de la Comision Geologica de Mexico. No. 

 1, Mexico. 1895. Pp. 55, plates sxiv. 

 In this publication, the authors confirm the ex- 

 istence of the Jurassic System in Mexico. They 

 note that the formation has a vast extent, 

 greater than is commonly believed, partly for 

 the reason that the localities are widely sepa- 

 rated and difficult of access. The fossils also are 

 scarce and not well preserved. Another cir- 

 cumstance which appears to be unfavorable to 

 the recognition of the system is its gradual pas- 

 sage into the overlying Cretaceous. This transi- 

 tion zone is barren of fossils or at best contains 

 forms which are of difficult interpretation. The 

 Jurassic rocks belong mostly to the upper divi- 

 sion, but localities exist in which strata are 

 found representing the middle and lower mem- 

 bers. Some authors, deceived by the resem- 

 blance of the Cretaceous limestones to those of 

 the Jura, have referred these deposits to the 

 Jurassic, but our authors have referred them on 

 the evidence of their contained fossils to the 

 Cretaceous on the geological map of the Ke- 

 public. 



