Tuomson.—On the Cleansing of Towns. 57 
Drs. Letheby and Williamson of the soil of its bed, both in Woolwich Reach 
and near to the sewage outfalls; and to give his consideration to the changes 
thus shown to have taken place in the channel of the river, and in the 
character of its bottom, for the purpose of reporting thereon. Captain 
Calver adds, that from the time of receiving the foregoing instructions, 
he had been engaged upon the various details of investigation, including, 
amongst other things, repeated observations upon the movements of the 
streams in the central section of the Thames, with the collection of such 
other physical facts as were likely to aid him in arriving at a clear under- 
standing of this important and interesting case*. 
From his report we shall make extracts, noticing the salient points 
of interest. He states “that the general features of Mid-Thames, its 
sectional capacity, and the various details of increase and decrease, are 
all brought out very clearly in the surveys made by the order of the Board. 
This series—the work of the same observers, and all referable to a common 
standard —has been made between 1861 and 1876.” 
Again: * It having been reported in 1867 that a vessel had unexpectedly 
touched the ground while passing the southern outfall, a new survey was 
ordered to be made for the locality." 
Again: “1832 to 1861, a considerable increase in the general capacity 
of the channel occurred in the foregoing period—the result of dredging, for 
the most part." 
Again: “1863 and 1864, sewage began to be discharged from the out- 
falls." 
Again: ** Since the Metropolitan outfalls came into operation, the former 
deep and free frontage of the southernmost one has lost a quarter part of its 
low water contents." Again: “that the upper part of the river has been 
troubled with accumulations, which, as will be shown, must necessarily have 
been conveyed upwards by the flood-stream.” 
In the analyses made, * the mud in each case was black and fetid in a 
state of active putrefactive decomposition, and, when examimed under the 
microscope, it was found to consist of broken-up sewage matter.” Of the 
water, when near Woolwich, Greenwich and London Bridge, “ all the 
samples were black and offensive, and they were found, on examination 
under the microscope, to consist of amorphous matter of the disintegrated 
tissue of vegetables, especially of wheat, and swarms of diatomaceous re- 
mains,” Again: in the last test of 1875, “ most of the samples demonstrated 
the presence of sewage.matter in a state of decomposition." Those from “the 
Gallion Reach, within the influence of the northern outfall, exhibited 
organic and other similar matter to those of street-mud, while others in the 
* Report, 15th October, 1877. 
