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Proceedings of Societies . 
Actinometra. They both agree in referring forms with a (sub) 
central mouth, five equal ambulacra, and no terminal comb on 
the oral pinnules, to Antedon. On the other hand, species with 
an eccentric mouth, a variable number of unequal ambulacra, 
and a terminal comb to the oral pinnules, belong to Actinometra . 
Chemical Society, February 6. — Dr. J. H. Gladstone, 
F.R.S., President, in the chair. 
Dr. Frankland opened a discussion on a paper read by Dr. 
C. M. Tidy on December 6th, 1878, “ On the Processes for 
Determining the Organic Purity of Potable Waters.” In the 
course of a long address Dr. Frankland said that he entirely 
dissented from Dr. Tidy’s suggestion that non-volatile matter 
may be removed mechanically during evaporation. He had 
proved by adtual experiments that mechanical removal only took 
place during violent agitation or the breaking of gas bubbles at 
the surface of the liquid. He was still more astonished, how- 
ever, to find Dr. Tidy, who is a physician as well as a chemist, 
suggesting that the poisonous constituents of sewage may be 
volatile. All the knowledge we have hitherto acquired about 
the infectious matter of epidemic disease pointed, he said, to 
the inevitable conclusion that the propagating material is not 
merely organic, but organised ; and that its virulence, unlike that 
of arsenic or other similar poisons, resides in its vitality and its 
power of multiplying itself almost indefinitely in the human 
body. An organised liquid, gas, or vapour, was a physical 
impossibility, and hence there is no foundation whatever for the 
opinion that the poison of sewage is volatile, or that it is not 
contained in the residue left on evaporation. With regard to 
the albuminoid ammonia process, Dr. Frankland’s experience 
coincided with that of Dr. Tidy. It had been put forward as 
capable of answering the question, “ Is the water wholesome or 
is it not ?” It did not, however, answer this question : It con- 
demned water containing only peaty matter, and it acquitted 
water containing urea and uric acid ? Could anybody believe 
that in 1876 the Chelsea Company’s water, drawn from the 
Thames, was “ safe ” in January, “ dirty ” in March and August, 
“safe” again in November, and “of extraordinary purity” in 
December, when it contained no less than 0*423 part of organic 
elements in 100,000 parts of water ; and when three other 
samples drawn from the same source were denounced as 
“ dirty” by the same process. Again in 1871, whilst the West 
Middlesex Company’s water was “ of extraordinary purity ” in 
January, April, and May, the Chelsea Company’s water was 
“ dirty ” in those months, although quite “ safe ” in December. 
Floods undoubtedly make Thames water dirty, but the albuminoid 
ammonia curve pursued the even tenor of its way quite regard- 
less of them. Dr. Frankland cordially agreed with Dr. Tidy’s 
strictures on superficial and rapid analyses of waters, in which 
