91 
The wonderful capacity for binding the sand dispiayea 
by the porcupine grass (Triodin. spp.) can be favourably 
compared witli that of Sji'niife.r Inrsuns on the dunes of our 
sea shores. 
Travertine. — Travertine was only found as small, local, 
surface coverings, most frequently along the banks of creek 
beds, where it is regarded as a valuable guide bo sub- 
terranean water. Examples occur along the course of Op- 
parinna Creek and certain creek beds in the Tomkinson 
Ranges. 
Travertine was further noted in many instances to overlie 
diorite dykes, a breccia having often resulted from the cemen- 
tation of originally loose rubble derived from the dykes (Op- 
parinna). The travertine occurring at the foot of Mount 
Davis, in the Tomkinson Ranges, deserves notice on account 
of its extreme compactness and hardness, it being almost 
resistant to the blade of a knife. At Stuart's Creek a small 
deposit of banded travertine has been produced by the pre- 
cipitation of successive layers differently coloured by varyiag 
magnesian and carbonaceous contents. 
A thick incrustation of calc-tufa was discovered in the 
Musgrave Ranges. To the west of Opparinna Spring a series 
of lock waterholes is to be found along the bed of a rugged 
gorge enclosed by steep walls of gneiss. One of such holes is 
situated at the base of a waterfall that has been produced by 
the intermittent flow of a creek over a locally hardened band 
of blue garnetiferous gneiss, the softer rock below having 
become undermined. This deposit of earthy, calcareous sin- 
ter, with a fair percentage of included organic matter, occurs 
as regular stalactitic and mammillated masses, hanging from 
the under side of the indurated ledge or bank of gneiss. The 
formation produces an imposing aspect. 
APPENDIX. 
Petrolog^ical Notes on Rocks Collected on the 
Expedition. 
Granite. 
Locality. — Mann Rangi^es, outcrop fourteen miles west of 
Mount Samuel. 
Macroscoijicallii. — Granitic, porphyritic ; the felspar oc- 
curring as large (up to 2'7 cm.), more or less lenticular, 
porphyritic crystals, rounded by the chemical ( ?) corrosion of 
the rock magma. Felspar dark grey, fresh, in places not un- 
like the greasy-looking elaeolites of syenites. 
