u 



(JlANTS A^J) PIGMIES. 



I ii 







No rocks appear outcropping. We must fieo them if tlipy are 

 to b(J found. In an obsc.i'o and unsanitari/ corner at its base, 

 in the vicinity of old houses, we observe something like rocks, 

 picking our steps we reach them. Our pick shows them to 

 be gypsum, — ttive Phister of Paris. This is perfectly satis- 

 factory, we know our geological position, we are on the same 

 horizon as we were in the vineyards of Herblay near Bt-au^ 

 champ. Wo arc geologically a/>(9re the Sables de Beauchamp, 

 and the " npper Nummuiites," the Calcaire (limestone) de 

 Saint Ouen, the marnes (marls) with plwladomija ludensis, and 

 the Travertin de Chanipigny. .Standing at the foot of Mont- 

 martre we stand geologically higher than if we stood on the 

 lofty nummulitic Peaks of the Pyrenees, the Alps or the 

 Himalayas (Vide preceding Nos.) AVe now climb the hill in 

 search of other deposits overlying the gypsum. High up we 

 find clay or marl exposed by a recent rainfall. In this we 

 have a prize^-a bed of pigmean oysters. These measure from 

 i;^ to 1| inches in width and 1^ to 1| inches in height. They 

 have unusually long Inlls, and hence are called odrca lonfjiro^- 

 tris. The stratum of clay is about 3 feet thick. We have 

 missed what comes between this and the gypsum. The 

 missing is well developed at Buttes Ch-mmont. It is called 

 Calcaires de Brie Meulieres. Tb.is supplies trie Buhrstones — 

 millstones, so much prized by flour millers of Canada and 

 elsewhere. Thtise millstones are replete with Charae, aquatic 

 plantti which have all the simplicity of ahjae. They emit a 

 fetid effluvium which is said to cause the malaria of the 

 Ct'.mpagna of Rome, where these plants al)ound. The Calcaires 

 de Brie is "a fresh water formation." Higher up the hill, 

 above the oyster bed, we find a yellow marl which is full of 

 the casts of sea-shells having Cyre/na convexa, Natica eras- 

 scdiim. These wi^' the oyster shell marls are "so-called" 

 Sables de Fontainebleau. The gypsum which constitutes the 

 principal rock of Montmartre is a hydrous sulphate of lime, 

 i. e., it contains a certain quantity of water. It can be 

 scratched with the finger-nail. Its texture is crystalline 

 lamillar, fibrous, granular, saccharoid, &c. Its colour is gen- 

 erally white — of this was mad the original "plaster of Paris." 



