qf iJie'^nv'tromofParh. 4d 



vhited, we ^baU mention Meudon, The chalk is bere co» 

 vered bv plastiq cl2fy and coarsu limestone. Tbe upper )iart 

 of this nia!?s is as it were broken, ^nd presents a kind 

 of rubble {brt\he), the fragments of which are chalk, and 

 the nitervals clay. 



The highest part of the mass of cha!k appeared to us to he 

 abovf the glasses ork of Sevres, li is 13 metres (494 feet) 

 above the Seir.e. This disposition raises up all the strata of 

 soil which surniouiJt it, and seems at the same time to di-' 

 roinisli their thickness. The mass of stone is sensibly in- 

 clined towards the banks of the river 



At Bouiiival, near Marly, the chalk is almost enfire1yex-^ 

 postd in some places, being only covered by calcareous 

 siones of a very fine grain, but in fragments more or less 

 large, and scattered \\\ a marley sand, which is almost purp 

 at the top. 



Amid.^t these fragments we find geodites, of a yellowish- 

 white limestone, compact and (ine grained, with sparry 

 ianiinse, and small wavities strewed with very small crystaU 

 of carbonated lime. The paste of these geodites contains a 

 multitude of small spiral univalve shells ; which seenis to 

 prove that this limestone does not belong to the chalk for- 

 mation. 



Among these geodites we found one, which presented a 

 large cavity fringed \\'\i\\ long and acute limpid crystals, 

 upwards of two centimetres ("79 inches) long. 



Mechanical division alone informed us, that these crystals 

 belonged to the species of sulphated stroniian, and a mor^ 

 attentive examination of their form instructed us that they 

 constituted a new variety. M. Hauy, to whom we com- 

 municated the circumstance, called it apotamous sulphated 

 ^troniian. 



These crystals present rhomboid al prisms with four 

 panes, the antics of which are the same with those of th$ 

 prism of the unitary, or blunted [emovssLe) varieties. Sec, 

 2« e.77^ / and 102° 5S'. They arc terminated by pyramid* 

 with four faces and very acute. The angle of incidence of 

 the faces of this pvramid on the adjacent panes is 161^ 16'. 

 The faces are produced by a decrement by two ranges to th«; 

 left and right of the angie E of the subtract! ve molecule. 

 This is a law which had not hitherto been recognized ia. 

 the varieties of sulphated stronlian examined, to this day. 



Its sign will be E E^ 'E. 



The crystals of strontiun hitherto observed In the envi- 

 rgns of J^i^ris are extremely small, and fringe the sides of 



some 



