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movements are mainly in one direction, while cholera may be moving in various
directions.
189. As regards the evidence of cholera movement to the south-east of the
endemic field, I shall merely state that the tables in the Appendix show that the
Military Stations in British Burmah felt the influence of the new emanation of
cholera in Bengal in 1859 and 1863, just as much as did any stations in the south-
western or northern " highways;" and as regards the years 1868 and 1869, the
Appendix to my cholera report for 1869, and the report of the Sanitary Commis-
sioner of British Burmah, both testify to the fact of a new invasion of the river
valleys in Burmah in that year. From other sources I have satisfied myself, that
the cholera in China of 1860 was a direct continuation of the south-eastern
overflow, and I infer also that the cholera of 1864 at Singapore and other parts
of the Straits Settlements was a direct contimiation of the epidemic invasion of
Burmah in 1863.
The last we hear of the 1868-69 invasion m British Burmah was a southward
extension through the Tenasserim Provinces. The Sanitary Commissioner
distinctly states that the dates of progress show that the epidemic " was travelling
south," after the invasion of Mergui.
190. Before the scientific world can accept a theory that seeks to explain the
spread of cholera to places so geographically remote as Peshawar and Singapore
by the agency of monsoon winds, it will seek to know something about the direc-
tion and rate of progress of such winds, in connexion with the progress of
cholera. It is manifest that the same winds that take cholera from Bengal
to the Punjaub, cannot be instrumental in sowing the seeds of cholera over
Burmah and China in the south-east.
The greatest obstacle to the reception of the monsoon theory of cholera inva-
sion is, I think, the unquestionable fact that cholera is not checked in its movement
by the prevalence of a strong monsoon wind blowing against its line of advance.
The narrative of Scott of the 1818 epidemic, and the record at pages 18 and 20
of the 1859 and 1864 invasions are quite clear, as regards the movement of former
epidemics. The southward and slightly eastward advance of the 1869 invasion
in this Presidency was certainly not checked by the south-west monsoon, nor did it
travel any faster when the monsoon turned round in its favour. That monsoon
moisture favoured the multiplication of the cholera miasm is quite probable, but
there is no evidence that prevailing winds checked or hurried the invasion. It is
a fact too, beyond all question, that the southward advance of this same epidemic
from Tinnevelly to Ceylon in 1870 was not checked by the strong southerly winds
then blowing. It follows, therefore, that there is a movement of cholera independ-
ent of strength or direction of winds, and that aerial influences cannot be so all-
powerful as indicated by Bryden.
191. I by no means wish to deny that the materiel for cholera propagation may
not be conveyed to a distance by the atmosphere. Knowing how far sensible par-
ticles from the earth's surface may be moved, especially during certain electrical
conditions of the atmosphere, by rotatory currents of air, I think it is very
probable indeed that solid particles of cholera contagium, as of small-pox or any
other contagium, may be thus transported from place to place ; and it is possible
also that the monsoon winds, which are moist, may have the power of carrying
them for a limited distance, but there has been no relation shown as yet between
the velocity of movement of cholera, and of monsoon winds. It is abundantly
clear that the development of cholera in a province has no sort of relation to