340 PROCEEDINGS OF SECTION C. 



force, and at the same time act as a lubricant to the blocks of 

 fetone. The cohesion of the rock being thus brought to the 

 lowest possible pitch, it requires but the starting force to 

 enable it to continue the motion clown hill, the sides of which 

 are too steep for the loose mass to rest on. The numerous 

 cracks and joints collect an immense quantity of water, which 

 being dammed back by the clay result in springs which are the 

 sources of the creeks. Years of slow chemical action prepared 

 the rock for its final dislodgement ; the unusual pressure of 

 water, owing to the great rains, soaked the ground and 

 started the mass moving, the weight of the superincumbent 

 material on an incline doing the rest ; the more or less rotten 

 boulders knocking up against one another provided the slurry 

 and debris that has, for the time being, ruined some acres of 

 lower-lying land, the quantity of rotten rock showing the 

 extent of decomposition the hill has been subject to. The 

 land having been loosened and removed its locality is drained, 

 but where the water is stagnant evidences of chemical action 

 are still to be seen in the ochreous deposits, the smell of 

 sulphuretted hydrogen and the iridescene on the surface of 

 the pools due to minute crystals of iron pyrites. 



6.— THE APPLICATION OF PHOTOGRAPHY TO 

 GEOLOGICAL WORK. 



By J. H. HARVEY. 



In the paper under the above heading which the author 

 read at the Melbourne meeting, the use of photography in 

 connection with geology was pointed out, and the many 

 branches of it which might be pressed into the service of 

 the geologist were enlarged upon, one of the branches 

 recommended being the practice of " stereoscopic work." 



For giving a correct impression of irregular country and 

 horizontal distances the value of the stereoscope cannot be 

 over-estimated. 



An ordinary flat photograph, the point of view of which 

 has been well chosen, and the lighting of which has been 

 carefully studied, gives a slight idea of the separation of the 

 various horizontal planes ; but a true rendering of this sepa- 

 ration, such as would be apparent on a personal inspection, 

 cannot possibly be obtained by the examination of anything 

 but a stereograph. 



Among the most interesting fossils which the author has 



