The seasonal periodicity of bad conduct in prisons is of interest as showing that we cannot account for psychic periodicity by invoking exclusively social causes. This theory of psychic periodicity has been seriously put forward, but has been investigated and dismissed, so far as crime in Holland is concerned, by J.R.B. de Roos, in the Transactions of the sixth Congress of Criminal Anthropology, at Turin, in 1906 (_Archivio di Psichiatria_ fasc. 3, 1906). The general statistics of suicides in Continental Europe show a very regular and unbroken curve, attaining a maximum in June and a minimum in December, the curve rising steadily through the first six months, sinking steadily through the last six months, but always reaching a somewhat greater height in May than in July.[164] Morselli shows that in various European countries there is always a rise in spring and in autumn (October or November).[165] Morselli attributes these spring and autumn rises to the influence of the strain of the early heat and the early cold.[166] In England, also, if we take a very large number of statistics, for instance, the figures for London during the twenty years between 1865 and 1884, as given by Ogle (in a paper read before the Statistical Society in 1886), we find that, although the general curve has the same maximum and minimum points, it is interrupted by a break on each side of the maximum, and these two breaks occur precisely at about March and October.[167] This is shown in the curve in Chart 6, which presents the daily average for the different months.