16 HENRY DEANE. 



sized joints with ironbark flitches, twelve by five inches, and four- 

 teen by seven inches, prove the highest efficiency for this joint. 



Monier System of combined concrete and steel construction. — 

 It is well known that the above system has been somewhat exten- 

 sively used for the construction of the sewerage aqueducts over 

 Johnston's and White's Creeks. In August last year the arches 

 were put to test, and it is satisfactory to find that the structures 

 in both cases were entirely successful. 



Purification of Sewerage. — Mr. Davis, Engineer for Sewerage 

 Construction has furnished me with the following particulars : — 

 In sanitary engineering perhaps the most important and certainly 

 the most interesting development, is in the purification of sewage. 

 When cheap land was available, conveniently situated, preference 

 has been given to broad irrigation. When the area was sufficient, 

 the soil suitable and the management good, excellent results were 

 obtained, but where circumstances were not favourable, some 

 other methods of dealing with the sewage requiring less land had 

 to be looked to. Among these is the method known as precipita- 

 tion and filtration. The sewage is allowed to flow into settling 

 tanks, after in most cases having had lime, or some other chemical 

 added to facilitate the precipitation of the suspended matter. The 

 effluent passes from the settling tanks to the land, or into com- 

 paratively small artificial filters, composed of sand, breeze or 

 other substances having the capacity of absorbing oxygen and 

 allowing large quantities of sewage to pass through it without 

 becoming clogged. In both these cases a good effluent can with 

 care be obtained, but the working expenses are high. 



The chief trouble and expense in the last named process has 

 always been the treatment and disposal of the sludge taken from 

 the precipitating tanks. In places near the sea-board it has been 

 punted out to sea, but in other localities it has become necessary 

 to use machinery to extract the liquid from the sludge, after 

 which the latter has been either carted away for use by the sur- 

 rounding farmers or disposed of in a destructor. It has been felt 



