328 
was observing. By a necessarily rough judgment, the angular 
motion as compared with the angular value of the field-bar,. 
would be about 1 minute of are. This is as if a flag-pole 20ft. 
in height vibrated through a space of =z1n. at the top. 
Now, in apparent opposition to the conclusion to be drawn 
from the foregoing as to the minuteness of the shocks, we 
have certain well avouched facts. I first take the somewhat 
startling circumstance reported in the Launceston papers by 
Mr. Geo. T. Hudson, as observed by him during the strong 
tremor of 13th December, 1883. He says:—“ Our attention 
was directed particularly to the mud-flat” (in the river) 
: “which was a state of rapid agitation, moving ap- 
parently up anc down in a most remarkable and alarming 
manner, the motion apparently coming from beneath, and from 
N.W. to. S.E. The rapid motion continued for fully one 
minute, and then gradually lessened, until it finally 
ceased. The wave motion was exceedingly severe, the tide 
being very low, ete.” It is not surprising that such a sight as 
this should impress the beholder with the idea that it must 
be caused by some very violent agitation. I think, however, 
that it may be explained without any such inference. The 
tide was low, the mud-flat was still wet and glistening, and 
of course it reflected vividly the rays of sunlight. Under 
these circumstances the smallest motion of the surface would 
be immensely magnified, the magnification increasing with the 
distance from which it was viewed, in addition to the fact 
that the deviation of the reflected ray would be doubled by 
reflection. On this very occasion I was with a party taking 
tea, in a summer-house in a garden almost adjoining the spot 
from which Mr. Hudson viewed the phenomenon, and yet the 
tremor passed totally unperceived by any of us. 
The shake of 13th July, 1884, was unquestionably by far 
the greatest shock of the whole series, and the only one that 
I know of that furnished any permanent and unquestionable 
exhibition of its violence. The principal tokens it left 
behind, in Launceston, were the throwing down a finial from 
the top of one of St. Andrew’s Church spires, and the dis- 
placement of the masonry of another by about an inch, the 
throwing down of the newly-erected chimney of a bakery, 
also the top brick or tile of the chimney of Mr. Lay’s house. 
All these effects however, may, I think, be accounted for 
without supposing anything more than a very minute 
shaking. (See M.S.) 
On the day following, I visited some of the china and glass 
warehouses, where I saw goods so piled that I should have 
thought that merely walking heavily across the shop would 
cause a smash; yet I> was told that nothing had been dis- 
turbed. In fact, I was informed at Mr. Hubbard’s establish- 
