XXXII. NORMAN SELFE. 



in gold dredge engineering, for some of the particulars quoted. It 

 is pretty well known I think, that several of our engineering 

 works are busy not only on bucket dredges for gold winning, but 

 that they also have in hand modifications of the centrifugal pump 

 dredge, for raising auriferous wash dirt. In these pumps special 

 provision is made to allow very heavy boulders to go through 

 without injury to the revolving vanes of the pumps, and numbers 

 of improvements in their details are suggested and introduced, 

 With the ladder dredges on the other hand, apart from the gold 

 saving appliances, the plant proper is often far behind the govern- 

 ment dredges of forty years ago. 



Compressed Air. — It does not appear that the use of compressed 

 air, to give motion to machinery, can be traced back earlier than 

 the year 1840, therefore it could have played no part in our first 

 settlers struggles with nature. As the motive power for rock 

 drilling however, and also in connection with coal mining, com- 

 pressed air has for a long time had an extensive application; and 

 now, not only is its general use extending for all kinds of power 

 transmission, but in two special directions it has recently advanced 

 by such phenomenal strides as to command our particular 

 attention. 



Without losing sight for one minute of the fact, that the 

 electrical transmission of power possesses many advantages which 

 do not appertain to other systems, very strong opinions are held 

 by practical engineers, that compressed air has been neglected a 

 good deal, because there is not about it that glamour of mystery 

 and intangibility which surrounds electricity. This halo of 

 mystery, combined with much popular ignorance and delusion 

 with regard to the mechanical power required for the generation 

 of electric energy, (the average man on the street believing it is 

 obtained from nothing and produces itself) has enabled the capital 

 required for enormous electrical enterprises and experiments to be 

 easily raised. The President of the Electrical Association in his 

 opening address last month, expressed himself as very much of the 

 same opinion. Compressed air has certainly in some instances, 



