PAS 



interposition of very numerous and 

 minute septa, transversely disposed. 

 The tubes are placed perpendicularly 

 round the centre, and it appears that 

 round the first formed tube, or 

 chamber, successive increasing co- 

 lumnar tubes were disposed, fold- 

 ing over each other at their ends. 

 "Whether these several tubes were 

 internally connected with each other 

 or not, or whether the chambers 

 communicated, or not, with each 

 other, by a siphuncle, are questions 

 not yet clearly ascertained. Like 

 some of the nummulites, this body, 

 when polished, has more the ap- 

 pearance of bone than of shell, and 

 from this and other circumstances, 

 it seems to approximate nearer to 

 the nummulite than to any other 

 fossil. 



FA'SSAITE. (from Fassa in the Tyrol.) 

 Called also Pyrgom. A mineral, a 

 dark-green variety of augite ; it is 

 also found in Scotland and Ireland, 

 in beds of primitive trap, limestone, 

 and magnetic ore. 



FASTI'GIATE. j (fastigiatus, Latin.) 

 FASTI'GIATED. j Pointed; a term 

 applied to a stem, peduncles, umbel, 

 &c. 



FAT OJJABTZ. ] (The Quartz hyalin 

 FETID QTJAETZ. ) gras of Haiiy.) 

 Quartz, both crystallised and mas- 

 sive, sometimes exhibits, when 

 fractured, a greasy polish on the 

 surface, equal to that which would 

 be produced by rubbing it with oil : 

 it sometimes, though not always, 

 gives out a fetid odour when 

 struck; from these two circum- 

 stances the above names have been 

 given to this variety. 

 FAULT, (faute, Fr.) A breaker 

 intersection of strata ; interruption 

 of the continuity of strata, with 

 displacement; the sudden interrup- 

 tion of the continuity of strata, in 

 the same plane, accompanied by a 

 crack or fissure, varying in width 

 from a mere line to several feet, 

 such fissure being generally filled 



[ 168 ] F A U 



with fragments, &c. Although the 

 two sides of a fault often come 

 into close contact, there is very 

 frequently a clayey substance in- 

 terposed which is impervious to 

 water ; and it rarely happens that 

 water on one side of a fault passes 

 to the other side. On the contrary, 

 the water is usually discharged 

 along the line of the fissure, par- 

 ticularly on mountain sides, in the 

 shape of springs. "When a fault 

 occurs in strata they are generally 

 either elevated or depressed, so 

 that in working a bed or vein there 

 appears to be a sudden termination 

 of it. Faults consist of fissures 

 traversing the strata, extending 

 often for several miles, and pene- 

 trating to a depth, in very few 

 instances ascertained; they are 

 accompanied by a subsidence of the 

 strata on one side of their line, or, 

 which amounts to the same thing, 

 an elevation of them on the other ; 

 so that it appears, that the same 

 force which has rent the rocks thus 

 assunder, has caused one side of the 

 fractured mass to rise, or the other 

 to sink. Of the extent of dis- 

 placement of strata some idea may 

 be formed from the following 

 statement; the old red sandstone 

 of the Fans, situated in South 

 Wales, is proved to have been 

 upcast to an extent of 700 feet. 

 Mr. Eald mentions that the great 

 south slip in the Clackmannanshire 

 coal field throws down the strata 

 1230 feet. If we suppose a thick 

 sheet of ice to be broken into 

 fragments of irregular area, and 

 these fragments again united, after 

 receiving a slight degree of irregular 

 inclination to the plane of the 

 original sheet, the re-united frag- 

 ments of ice will represent the 

 appearance of the component por- 

 tions of the broken masses, while 

 the intervening portion of more 

 recent ice represents the clay and 

 rubbish that fill the faults. In the 



