426 ©. G. Rockwood, Jr—American Earthquakes. 
and a few items, which were regarded as somewhat uncertain, 
are printed in smaller type. The division of the day into 
twenty-four hours is again employed. 
An attempt has also been made in these notes to distinguish 
the shocks according to the degree of intensity. For that pur- 
pose a scale was provisionally adopted, with reference to which 
the adjective indicating intensity was selected, this selection 
being guided, whenever possible, by the statements of the phe- 
nomena observed rather than by the mental impression of the 
observer. ‘Thus an earthquake called by the newspapers 
‘“‘severe” may perhaps be found characterized here as “light 
because only causing the phenomena which mark that degree. 
The scale employed is as follows: 
I. Very light :—Noticed by a few persons but not generally 
felt. 
Il. Light :—Felt by the majority of persons, rattling windows 
and crockery. 
Ill. Moderate :—Sufiicient to set suspended objects, as chande- 
liers, ete., swinging, or to overthrow light objects favorably 
aced. 
V. Strong :—Sufficient to crack the plaster in houses or to 
throw down bricks from chimneys. 
V. Severe :-—Overthrowing chimneys or walls and injuring 
some buildings. 
VI. Destructive :—Causing general destruction of buildings, ete 
This scale is adopted for the purposes of the present ar nee 
but it is quite probable that considerations of uniformity shah 
European observers may lead to the use of the Rossi-Fore 
Scale in future papers. 
1884. 
Jan. 3.—At 20" 40" a light shock oceurred at Portland, Or sa 
duration about two seconds; vibration southeast to northwest. 
U. S. Weath. Rev. 
Jan. 4.—At 11" 56" a very light shock at Los Angeles, Califor- 
nia.— U. S. Weath. Rev. Ld : 
Comptes Rendus, Feb., 1884 
* 
