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S. Holden (1846-1914) (Holden 1898) used it in his catalog of earthquakes in the
western USA, from which it descended to the listing of Townley and Allen (1939).
Compared to the former scales a refinement is clearly to be observed when it
comes to the description and perception of damage. Description of damage starts
with intensity VI, degree X meaning completely destroyed. In Volger's scale, de-
grees 0-4 relate to damage zones, whereas degrees 4, 5 and 6 reflect merely per-
ception by humans. In the following years, all discussed events were given with
intensity degrees according to the Rossi-Forel scale. Forel even modified the events
he had already interpreted with the Forel-scale. This scale was in use until the
first third of the 20th century (Valone 1998). Giuseppe Mercalli (1850-1914), who
published a modified version, still with ten degrees, improved the scale. (He had
also published an earlier scale of six degrees, which was a modification of Rossi's
first scale). It appeared, though, that ten degrees were insufficient for expressing
the whole range of effects from the weakest to the calamitous. The Italian Adolfo
Cancani (1856-1904) therefore proposed the extension of the scale to twelve de-
grees. However, he omitted to flesh out his twelve degrees with full descriptions,
and restricted himself to titles for each degree (like 'destructive'), and estimated
ground acceleration values (Musson 2005).
What about the use of Volger's scale by his colleague Forel? The latter was
very well acquainted with Volger's work as he used it for statistical purposes
(Forel 1884). As what concerns the development of his own scale or the plotting of
intensity maps, it seems that Forel neglected Volger's contribution entirely. Volger
was never acknowledged by Forel or his collaborator Rossi. What's more, despite
these endeavors, August Sieberg in 1904 laments about the lack of any conven-
tional and internationally approved quantitative scale, analogous to those used in
meteorology (Sieberg 1904). Volger's work, we must conclude, was highly recog-
nized and debated by his contemporaries and successors in favor of his accomplish-
ments regarding earthquake theory, and the broad collection of his earthquake data
(Tams 1952), but not in matters pertaining to intensity scales and map plotting.
Acknowledgments
The authors would like to thank Duncan Agnew (UC San Diego), Katie
Fromberg (UC Berkeley), Gregory Good (West Virginia University) and an anonymous reviewer
for helpful comments on the paper.
References
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Annalen der Physik und Chemie 13/89
Forel FA (1880) Tremblement de terre du 30 december 1879, Jahrb ucher des Tellurischen Obser-
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