ON SEISMOLOGICAL INVESTIGATIONS. 59 
(2) The catalogue supplied by H. Masing, St. Petersburg, the 
makers of the pendulum and recording part of the instrument. 
(83) ‘ Ueber ein neues Aperiodisches Horizontalpendel mit galvano- 
metrischer Fernregistrierung,’ by Prince B. Galitzin. (4) ‘ Ueber 
einen neuen Seismographen fiir die Vertikalkomponente der Boden- 
bewegung,’ by Prince B. Galitzin. (5) ‘Die electromagnetische 
Registriermethode,’ by Prince B. Galitzin, Academy of Sciences, 
St. Petersburg. 
The Galitzin recorder for vertical movements operates electrically 
in exactly the same manner as the horizontal instrument, and a similar 
magnetic damper is fitted to it. The room in which the pendulum 
is placed must be maintained as far as possible at a uniform tempera- 
ture, as the change in the elasticity of the spring which supports the 
pendulum causes excessive wandering if the temperature changes by 
even as little as 0.5 per cent. 
Comparative cost.—A Galitzin installation is much more expensive 
than a corresponding Milne one. Two horizontal pendulums complete 
with galvanometer and one recording drum cost at least 148/., while 
the pendulum for vertical movements with galvanometer and drum 
costs at least 1101. 
This does not exhaust the expensiveness of the instruments, since 
about six times as much sensitive paper is required for one Galitzin 
recording drum as for one modern Milne drum for two pendulums. 
It is customary to run the paper at three centimetres per minute, and 
unless the optical arrangements were improved it would be hardly 
feasible to run it at much less speed without losing a good deal. 
Under these circumstances the cost in paper alone of one recorder is 
about 331. per annum. 
Attention required.—The Milne instrument does not require more 
than ordinary skilled attention. If the operator be used to handling 
_ delicate instruments little more is required. Of the Galitzin instrument 
the same may be said as far as the ordinary routine is concerned, but 
the greater complexity of the apparatus means a greater number of 
_ things liable to go wrong, and sooner or later it is almost certain 
‘to happen that highly skilled attention is necessary. Both types of 
instrument require periodical standardisation, but while in the Milne 
_ type this is quite a simple process, in the Galitzin it is quite otherwise. 
A certain amount of auxiliary apparatus is required, such as telescopes 
and scales, and two persons are necessary to make simultaneous obser- 
vations of the pendulum and galvanometer; when these have been 
made the constants of the instrument can be determined. Prince 
_ Galitzin has worked out formule for this purpose. 
__ The whole process has in general to be gone through twice for each 
Instrument, and it is a lengthy operation, taking probably about two 
working days. A certain measure of observational skill is required to 
take the necessary readings accurately, as well as a fair working know- 
ledge of mathematics to deal with the results when obtained. 
Tt would be possible to simplify the process somewhat more 
than has at present been done, and reduce it largely to routine; but 
