ON SEISMOLOGICAL. INVESTIGATION. 221 
which the records are made being only about a franc or a franc and a half 
a month. 
2. Any person can superintend and adjust them easily. 
3. They are not subject to the displacement of the zero-line. 
4. Owing to the great velocity which can be given to the paper, the 
epoch of the different phases of the movement can be determined with 
great accuracy. 
5. They allow all the minute details of the movement to be studied. 
It is obvious that these, especially the two last, are great advantages. 
On the other hand, the long pendulums are subject to several objections 
as compared with the horizontal and bifilar pendulums. 
1. Owing to their great length (Professor Riccd’s seismometrograph 
at Catania is 26 metres long), they are difficult to install, and indeed 
require a building almost specially constructed for the purpose. 
2. They are much less delicate than the horizontal and bifilar 
pendulums. 
3. The latter are also adapted for other purposes—e.g., investigating 
the bending of the ground by barometric and tidal loading—and this will 
facilitate their adoption at astronomical observatories, where, from the 
ease with which the exact time can be ascertained, it is most desirable 
that they should be established. 
The instruments I propose to describe are: (1) Professor G. Vicen- 
tini’s microseismograph ; (2) Dr. G. Agamennone’s seismometrograph, 
(3) Dr. A. Cancani’s seismometrograph, and (4) Professor G. Grablovitz’s 
geodynamic levels. It will be seen that the first of these is more or less 
free from the above-named objections. 
Professor G. Vicentini’s Microseismograph.—An account of this instru- 
ment and the results which have so far been obtained with it is given in 
the following papers : 
1. G. Vicentini : Osservazioni e proposte sullo studio dei movimenti microsismici: 
‘ Atti della R. Accad. dei Fisiocritici’ (Siena), vol. v. 1894. 
2. G. Vicentini: Osservazioni sismiche (two papers): bid. 
3. G. Vicentini: Movimenti sismici registrati dal microsismografo nella prima 
meta del luglio 1894: Zbid. 
4. M. Cinelli: Sulle registrazioni del microsismografo Vicentini avute a Siena 
del 15 luglio al 31 ottobre 1894: Tbid. 
G. Vicentini: Microsismografo a registrazione continua: Cenno sui movimenti 
sismici dei giorni 14 e 15 aprile 1895: ‘ Bull. della Soc. Veneto-Trentina di 
Scienze Naturali’ (Padova), vol. vi. 1895, pp. 5-12. 
6. G. Vicentini: Microsismografo a registrazione continua: ‘Boll. della Soc. 
Sismol. Ital.,’ vol. i. 1895, pp. 66-72. 
7. G. Vicentini: Intorno ad alcuni fatti risultanti da osservazioni microsismiche : 
“Atti e Mem. della R. Accad di Scienze, &c., in Padova,’ vol. xii. 1896, 
pp. 89-97. 
8. G. Vicentini and G. Pacher : Considerazioni sugli apparecchi sismici registratori 
e modificazione del microsismografo a due componenti: ‘ Atti del R. Ist. 
Veneto di Scienze,’ &c., vol. vii. 1896, pp. 385-399. 
9. G. Vicentini: Fenomeni sismici osservati a Padova dal febbraio al settembre 
1895 col microsismografo a due componenti: ‘ Atti della Soc. Veneto- 
Trentina di Scienze Naturali’ (Padova), vol. iii. 1896, pp. 3-63. 
5. 
Some further details with regard to the construction of the instrument 
are taken from two letters written by Professor Vicentini to Professor 
Milne. 
Professor Vicentini was led to design this instrument owing, he says, 
to the difficulty of obtaining good photographic registration, the incon- 
