574 president's address. 



to the northward of Grlen Innes and Tenterfield. It also occurs 

 in the Tumut and Adelong and Jingellic districts, as well as at 

 Mount Brown and in other parts of the colony. But nearly all 

 the ore hitherto raised has come from the New England mines. 

 This tin-field is so extensive that it will probably become one of 

 the most important in the world. The stream tin ore is 

 obtained from alluvial deposits which are of similar origin and 

 belong to the same Recent and Tertiary periods as the gold 

 drifts which I have already described ; and in the tin-bearing 

 deep leads, which are from 50 to 200 feet deep, we also find 

 numerous impressions of fossil leaves beautifully preserved, 

 together with casts of unto shells and fossil insects, specimens 

 of the latter, which are the second discovered in the colony, 

 were exhibited at our August meeting. 



The shallow deposits which have been so productive, are rapidly 

 becoming exhausted ; yet they still give employment to several 

 thousands of miners who are principally Chinese. 



The deep leads are being traced into deep and wet ground, so 

 that costly machinery is necessary for the proper working of them. 



With but little exception, the ore which has been sent to 

 market has been stream tin ; but lately considerable attention 

 has been paid to the development of some of the numerous lodes 

 which have been discovered. 



The lodes are very variable in their modes of occurrence : 

 sometimes the ore is found as thin veins of pure cassiterite ; at 

 others it occurs in quartz reefs, or as irregular masses in felspar, 

 or in separate coarse grains disseminated through porphyritic 

 granite. Some of the so-called lodes exhibit all these various 

 features. The principal formations traversed by the tin lodes, 

 are granite, porphyry, and metamorphic slates, sandstones and 

 conglomerates probably of Siluro-Devonian age. The minerals 

 associatedwiththetinore are, pyrites, mispickel, blende, wolfram, 

 tourmaline, fluor spar, bismuth, chlorite, etc. My colleague, 

 Mr. T. W. Edgeworth David, B.A., F.Gr.S., is now engaged 

 upon a Geological Survey of this tin field, and I anticipate that 

 the result of his labours will prove of great economic and 

 scientific value. 



