Yee 
BRANNER: THE STONE REEFS OF BRAZIL. 171 
VI. 
The Consolidation of the Stone Reefs. 
PAGE PAGE 
The cement. „en, e aa Т Ш. Lime carbonate from the 
Analysis of the rock... . „ 172 лор 
Microscopic examination . . . 178 Consolidated beaches of 
Origin of the cementing material 174 tie В, . v 187 
I. Cement from beach sands Relations of density to deposition 190 
by rain-water or spray . 175 IV. The seaward percolation 
IL Lime carbonate from the of acid land-water . . 192 
OGAN и q Ш Possible influence of cli- 
Cog of volcanic origin . . 178 Wat сс сз, ДВ 
Со» from sea-water . . . 182 'The process not a continu- 
Is the process universal? . 184 OUS 008 =.» s «s 10d 
CONGO TY у с 1 
Havına studied the forms and origin of the beaches, we may 
now consider the process or processes by which they may have been 
consolidated. 
That the ancient forms of the beaches of which the stone reefs are 
made have been preserved is due to the fact that the sands of these 
beaches have been firmly cemented. Without the hardening, we should 
have had no stone reefs, because the processes of beach changes would 
have failed to leave these old shore lines outstanding: they would 
either have been buried by later accumulations, or have been destroyed 
by wave action. 
Tug CEMENT. 
The hardening of the rock is due to the deposition of carbonate of 
lime in the interstices of ordinary beach sands. This is shown by a 
microscopic examination of fresh specimens of the rock (see page 173), 
and by putting & piece of the rock in an acid that will remove the lime 
carbonate. 
A chemical analysis has been made of a sample of the Rio Formoso 
reef rock, with the following results : — 
