110 
FACTS AND OBSERVATIONS. 
it is placed in heaps into a kind of tank-like hole dug into the 
soil, care being taken to line its bottom and sides with straw. 
When filled the heap is first lightly covered with straw and 
then with earth—in fact, arranged in the manner used for 
preserving potatoes, carrots, &c. From the testimony of 
competent agriculturists and veterinary surgeons, the process 
here alluded to is indeed to be recommended for its good 
effect upon the cattle fed by vegetable matter thus pre¬ 
served .—•Chemical News . 
A New Theory of Nervous Action. —This theory, 
which was put forward some time since by Dr. Robert 
AFDonnel, and escaped our notice, we now call attention to, 
for it is very remarkable, and worthy of serious consideration. 
The paper was read before the Royal Irish Academy. The 
theory is thus stated by the author :—“1 conceive that the 
various peripheral expansions of sensitive nerves take up undu¬ 
lations or vibrations, and convert them into waves capable of 
being propagated along nervous tissue (neuricity,as it has been 
named). Thus, the same nerve tubule may be able to trans¬ 
mit along it vibrations differing in character, and hence giving- 
rise to different sensations; and, consequently, the same 
nerve tubule may, in its normal condition, transmit the wave 
which produces the idea of simple contact, or that which pro¬ 
duces the idea of heat—or, again, the same nerve tubules in 
the optic nerve which propagate the undulations of red may 
also propagate, in normal vision, those which excite the idea of 
yellow or blue, and so for other senses. I advocate this 
undulatory theory of sensation in preference to the theory of 
distinct conductors—1st, because it is simple. 2ndly, because 
it is strongly supported by analogy, when compared with wave 
propagations in other departments of science. 3rdly, because 
it appears to be in harmony with a large number of recognised 
physiological facts, which seem inexplicable upon the theory 
of distinct conductors .”—Popular Science Review. 
Iron as a Filter and Deodoriser,— Attention has 
recently been called to the use of spongy iron as a deodorising 
material, which Dr. Voelcker considers of greater potency 
than animal charcoal. Sewage water passed through a filter of 
this substance is completely purified, and this filtered water, 
after having been kept six months protected from the air, was 
perfectly sweet, and free from any fungus growth. The 
spongy iron is obtained by calcining a finely divided iron ore 
with charcoal. Mr. Spencer, whose name is connected with 
the discovery of the electrotype, has for some time been advo¬ 
cating the use of a filter of this description. Its power of 
