Reviews—. Gossele-—Phosphate beds N. of France. 563 
ashes composing the high central plateaux of Mau, Kamasia, and 
Lykipia have evidently issued from a north and south fissure. The 
site of this fissure is now occupied by the chain of lakes commencing 
with Naivasha on the south, and terminating northward in Lake 
Baringo. Along this line recent eruptions, some still giving out 
steam, have broken out, and it is the interception of the drainage by 
the material thrown out from these vents that forms the lakes 
Naivasha, Nakuru, and Elmeteita. 
- Highly acid and ultra-basic rocks are represented. Kilimanjaro 
and the Kyulu Mountains are chiefly built up of basic rocks, while 
the lavas of Lykipia and the Mau plateaux are chiefly acid. It 
appears that the latter localities have been the seat from which acid 
lavas have continued to be poured from times prior to the first 
eruptions of Kilimanjaro up to the present day. 
The basic lavas of Kilimanjaro do not extend very far from the 
original point of issue. At least this is so to the north, for no lavas 
were found on the plains of Lytokitok, distant thirty miles north of 
Kilimanjaro. On the other hand the acid lavas of Mau and Lykipia 
extend for great distances. Hastwards they stretch as far as the 
Athé plain, about fifty miles, and westwards to near the shores of 
Victoria Nyanza, a distance of nearly one hundred miles. 
Further westward, in Busoga and Buganda, basic igneous rocks 
pierce the metamorphic rocks, but without possessing any general 
trend. 
With the exception of the still active volcanoes it is impossible to 
state even the approximate geological age of any of the eruptions. 
Some of the volcanoes are possibly only dormant, others are certainly 
extinct, but none appear to be of great geological antiquity. All 
that can be safely asserted is that they are long subsequent to the 
deposition of strata containing Ammonites, for, whereas the con- 
glomerates of these sedimentary deposits contain pebbles of schist 
and gneiss, they nowhere yield fragments of igneous or volcanic rocks. 
RH VL HW S. 
I.—Notr sur LES GiTES DE PHOSPHATE DE CHAUX DES ENVIRONS 
DE E'RESNOY-LE-GRAND. Par M. Gossetet. Annales de la Soc. 
Géol. du Nord, vol. xxi. 1898, pp. 149-159. 
N this paper Prof. Gosselet describes the position and mode of 
occurrence of some newly opened deposits of phosphate of lime 
near Fresnoy-le-Grand, in the north of France. The workable 
deposits do not extend over areas of more than from five to ten 
acres in each locality, they occur in a zone of Gray Chalk of from 
14 to 2 metres in thickness, containing Belemnitella quadrata, Ven- 
triculites and sharks’ teeth. ‘The phosphate is partly in the form 
of concretionary nodules, which are so numerous as to form a sort 
of conglomerate in the lower portion of the bed; the phosphate 
varies in amount from 9 per cent. to 27 per cent. The Gray Chalk 
rests on White Chalk with Micraster coranguinum, and the upper part 
