318 EXPERIMENTS RELATIVE TO METEORITES. 



also, a silicate of a pyroxenic nature. This is the case in the meteorite of Toula, 

 government of Perm, in Kussia, the lithoid part of wliich atTects a very remark- 

 able breccia-form arrangement, as well as in that of llittersgriin, in Saxonv. In 

 the two types of syssiderous meteorite which have jnst been cited, the stone is in 

 o-rains disseminated and discontinuous. But it may happen that the stone therein 

 is continuous as well and at the same time as the iron ; that is to say, that the 

 mass ]-esults from the mutual entanglement of the two continuous systems, the 

 one metallic, the other stony. Such, among others, is the meteorite of Ritters- 

 gran. 



III. — METEORITES OF THE THIRD GROUP, OR SPORADOSIDEROUS. 



The greater part of the meteorites are characterized by a stony paste, in which 

 the iron, instead of being continuous, as is the two former groups, is dissemi- 

 nated in granules. The relation between the iron and the stone is then precisely 

 the inverse of that which characterizes the type of Pallas and of Atacama. 

 Each of these grains presents, moreover, the characters of composition and struc- 

 ture of the iron meteorites. Like them, they include nickel, and the phosphuret 

 and sulphuret of iron. The grains of iron, otherwise very variable in propor- 

 tion, have also very different dimensions, from that of a hazel-nut, or larger, 

 down to grains scarcely visible, or even microscopic. Their form is very irregu- 

 lar and frequently tubercular. 



In this series, the extreme terms of which are so remote, but which are con- 

 nected by a multitude of intermediate bodies, we may distinguish three sub- 

 groups. 



FIRST SUB-GROUP, OR POLYSIDEROUS METEORITES. 



In the first place, this sub-group, being the richest in iron, is represented by 

 masses which their miKcd cojuposition might lead ns to consider either as stone 

 or as iron. We designate them by the name of polysiderous, (-oAu?, much); the 

 metal and the silicates may exist therein in apparently equal volumes. Among 

 the meteorites pertaining to this sub-group we may particidarize that which was 

 foimd in Sierra de Chaco, Chili. The grains of iron in this meteorite, which are 

 very voluminous and of a tubercular form, yield with acids the remarkable fig- 

 ures which we have descrijbed. In this experiment it will be observed that each 

 grain is enveloped with a metallic pellicle more or less thin, the structure of which 

 is much more confused than that of the mass. It would seem that at the per- 

 iphery the crystallization had been embarrassed or troubled. The stony gangue, 

 in W'hich the metallic grains are imltedded, is essentially formed of silicates. If 

 studied more closely, it will be found to result, in general, from the mixture, in 

 variable proportions, of a basic silicate of magnesium, peridot, with a more acid 

 silicate, known by the name oi pyroxene. 



SECOND SUB-GROUP, OR OLIGOSIDEROUS METEORITES, (COMMON TYPE.) 



The meteorites incomparably most frequent enter into the sub-group at which 

 we now arrive. In ten falls, nine at least pertain to it ; hence it may Tte desig- 

 nated as the common type. We give to the meteorites which it comprises thf« 

 name of oligosidcrous, {nhyoc^ little.) 



These meteorites are easily distinguished by their stony aspect from those of 

 the preceding sub-group, and of coarse more readily still from those of the two 

 first groups. The fracture, ordinarily of an ashy gray and rough to the touch, 

 recalls strikingly that of certain finely-grained trachytes. The mass is entirely 

 crystalline, as the microscopic examination of a lamina sufficiently thin immedi- 

 ately evinces. The paste appears, at first view, almost homogeneous; but a 

 more attentive examination enables us to recognize that it results from a mixture 



