178 KEPORT — 1871. 



independently of surface preparation, it was soon found that the sewage 

 descended to the drains so rapidly as to prevent its profitable distribution on 

 the surface. It was stated to the Committee that when this effect was dis- 

 covered it was determined that the drains should be stopped by digging down 

 to them and plugging them, the result of which then was to keep the soil in 

 a state of saturation, and to allow the unpurified sewage to pass over the 

 surface into the stream. The engineer employed by the Commissioners has 

 since superseded this state of things by adopting the special mode of treat- 

 ment referred to, which consists of intercepting the existing drains at the 

 depths at which they were originally laid, and bringing the i;nderdrainage 

 water to the surface by outlet drains discharging into lower carriers for re- 

 distribution. 



At the time of the inspection by the Committee the lowest carriers were 

 receiving effluent liquid of an impure character from the surface, at the same 

 time that the underdrainage water was being discharged into them in the 

 way described. 



The land of the southern farm is not generally of so heavy a description 

 as that of the northern, though portions of it contain clay. Other parts are 

 peaty,, and are naturally very poor. Wherever the engineer has considered 

 it necessary to drain the subsoil, this has been effected in a mannei" similar 

 to that adopted on the northern farm. 



The striking features in the case of Tunbridge "Wells are : — 



1. Instead of concentrating the sewage at one farm under one manage- 

 ment, it has been divided, in accordance Avith the watersheds, into two parts, 

 involving two separate systems of works and management. 



2 . The main conduits and carriers are more than ordinarily substantial, 

 and are therefore expensively constructed ; and, following contour-lines on 

 the surface, have a tortuous course, and so must interfere with approved cul- 

 tivation. 



3. The character of the underdrainage, being designed for the redelivery 

 of the sewage on to a lower surface by drains gradually getting nearer and 

 nearer to it, must necessarily prevent alike a frequent and deep woi'kiug of 

 the surface-soil. 



4. The sewage being run over the surface of the land on the catch- 

 water system (by night as well as day), with the intention of reapplying the 

 overflow, its distribution is necessarily unequal both in quantity and qualitj', 

 the first land sewaged receiving more than it requires, while the last must 

 suffer from a deficiency imless there is a positive waste of sewage, as the 

 analyses really show that there is. 



These several features illustrate the advantage of combining with the 

 services of the civil engineer and the chemist those of the practical agricul- 

 turist when laying out a sewage-farm. If they were not pointed out by the 

 Committee thus early in the progress of sewage-irrigation, they might be a 

 source of disappointment and surprise to those who contemplate the utilization 

 of the sewage of their own towns by this the most profitable mode of treat- 

 ment at present known, when properly conducted. While saying this, it 

 is desirable to point out the siiperior character of the works carried out at 

 Tunbridge Wells, and at the same time to express approval of the enterprising 

 manner in which they have been undertaken by the Local Authority. 



