1884.] The Health Exhibitiom 583 
on the addition of a pinch of alum, seems to curdle or flake. 
In a few minutes the suspended matters go to the bottom, 
carrying with them no inconsiderable portion of the dis- 
solved impurities. Indeed the experience of the French 
troops in Tonkin shows that the microbia present, though 
not destroyed, are carried to the bottom, so that the clear 
supernatant water may be drunk with impunity. 
This brings us to one of the most interesting features in 
the Exhibition, — the process of the Native Guano Company 
for purifying sewage, waste waters, &c., before they are 
allowed to fall into the rivers. The sewage is mixed with 
clay and waste animal charcoal, a combination which power- 
fully absorbs the offensive matters dissolved in the water. 
Sulphate of alumina, or the corresponding hydrochlorate 
(hydrated aluminium chloride), is then added, which not 
only carries down with it the clay and carbon, with all that 
they have absorbed, but precipitates a very considerable 
proportion of the organic matters, whether such may be in 
suspension or solution. 
This process is to be seen at work daily, though of course 
on a very reduced scale. We cannot help referring to an 
error committed by a medical contemporary, who stated 
that vegetables grown with the manure produced by the 
Native Guano Company’s process were equal to those pro- 
duced by the irrigation system. This is exceedingly faint 
praise. As far as we have observed, vegetables grown on 
sewage irrigation farms are deficient in flavour and firmness, 
and soon pass into a very offensive putrefaction. 
Three firms engaged in the manufactory of sanitary 
earthenware — Messrs. Doulton, of Lambeth ; Cliff, of New 
Wortley ; and Wilcock, of Burmantoft — are distinguished 
for the high quality of their exhibits, not a few of which, 
however, though admirable in themselves, have no imme- 
diately apparent connection with public health. 
Painters’ colours are strongly represented. The firms 
Griffith and Co., Freeman and Co., the Torbay and Dart 
Paint Company (Limited), Turner and Sons, and Hare and 
Co., — all display series of colours understood to be free 
from all objedfionable ingredients. A reform in this respeCt 
has long been needed. White lead, which is so extensively 
used alone, and perhaps in even greater quantities in ad- 
mixture with other colours, is most injurious to the workmen 
employed in its manufacture, to those who use it, and in 
many cases to the inhabitants of houses to which it is 
applied. Lead has been characterised as the meanest, the 
most perfidious, of poisons. The victim who gradually 
