Se 
SG —=—  e  e 
ON SEISMOLOGICAL INVESTIGATIONS. 103 
now passes through two horizontal slits in these pieces of mica. A 
slit has also been made for the silk thread. These narrow strips of 
mica fixed to narrow cubes of wood, almost making a triangle, rest on 
the top of the clock box under the movable cover. The intention is to 
reduce the space to which the pendulum swings, and to prevent air 
movements as far as possible from acting on it. 
‘A small glass slide (microscope cover glass) has been fixed over 
the slit in the top of the clock box, under the blackened shield at the 
end of the boom, and a piece of glass fixed to the underside of the 
moyable cover. 
* Screens made of wood and American cloth have been temporarily 
placed round the seismograph. We intend having a large screen with a 
cover made to go round and over the instrument, so that the seismo- 
graph will be practically enclosed in an American cloth cabinet. 
‘The pieces of mica and asbestos were used first, and these reduced 
the tremors. When the screens were placed round the seismograph the 
tremors were further reduced, and when we obtain a new screen I 
am hoping things will be better still.’ 
Magnetic Observations at Falmouth Observatory.—Report of the 
Committee, consisting of Sir W. H. Preece (Chairman), Dr. 
W. N. SHaw (Secretary), Professor W. G. ApAms, Dr. 
CHARLES CHREE, Captain E. W. Creax, Mr. W. L. Fox, 
Dr. R. T. Guazeprook, Sir A. W. RtcKer, and Professor 
A. SCHUSTER. 
Tur usual number of absolute observations have been made by Mr. 
Kitto. The mean values of the magnetic elements for the year 1911 - 
are as follows :— 
Declination . 3 i x i . 17° 330 W. 
Inclination . 3 5 é . 66° 28-2 N. 
Horizontal force. : ¢ : . 0°18798 C.G.S. 
Vertical force i : : : ©? O3L72)045 
These results were deduced from the measurements of the curves 
made on the five quiet days a month selected by international agree- 
ment at de Bilt, the curves being standardised in the usual way by 
reference to the absolute observations. 
The measurements of the declination, horizontal force, and vertical 
force curves on the quiet days were also employed for calculating 
diurnal inequalities of these three elements and of the inclination which 
have appeared in the ‘ Report of the Observatory Committee of the 
Royal Cornwall Polytechnié Society for the year 1911,’ and in the 
* British Meteorological and Magnetic Year Book,’ Part IV. (2), pub- 
lished by the Meteorological Office. ay 
A-new suspension was fitted to the horizontal force magnetograph 
by Mr. E. Gold in July 1911, and for a few days thereafter the drift 
of zero in the instrument was too large to admit of satisfactory measure- 
ment of the curves. Under the circumstances it was decided to omit 
