GUPPY — SCIENTIFIC KNOWLEDGE IN TRINIDAD. 
81 
place to intermittent fever is less as the population is con- 
centrated ; the danger invariably diminishing in proportion 
to the density of the habitations. M. de Tournon shows 
from historical data that those parts of the Pontifical States 
which were unhealthy in 1810 (as they are now) were for- 
merly densely peopled and covered with habitations and were 
salubrious. At a later date when the local population had 
been destroyed and the Romans had been drawn oft in great 
numbers by incessant wars, unhealthiness began to arise 
from the depopulation and from the substitution of pasture 
for arable lands. By means of this hypothesis Dr. Tripier 
explains the continued exemption of Paris from intermit- 
tent fevers, in spite of the constant disturbance of the soil in 
that city in the course of the improvements going on there. 
These questions cannot yet be considered as approaching to 
a final settlement ; for to take M. de Tournon’s case, we 
know that there have been oscillations of level in Italy 
which may have increased the extent of swamp in that 
country. It would be interesting to learn from the medical 
men of these colonies how far the views expounded by Dr. 
Wood and M. Tournon are borne out here : and it would 
not be without importance to determine what the influence 
of trees may be in diminishing liability to fever. 
The other papers printed in the “ Proceedings” are enu- 
merated in the Report of your Secretary. There is only 
one other I shall touch upon, and that is the interesting 
memoir by Dr. Groding on the Petroleum of Barbados. I 
may remark in reference to this paper that although the 
Scotland formation of Barbados differs much in composi- 
tion from the Miocene beds of Trinidad, yet we have re- 
semblances in the occurrence of petroleum and other carbo- 
naceous deposits and of large quantities of selenite. More- 
