May 3, 1912] 
and method of presentation. The numerous 
illustrations are wisely chosen and well rend- 
ered and the few errors noticed in the text are 
mostly typographical. A misleading misprint 
occurs in the statement that the first success- 
ful dirigible balloon in 1885 sailed from Calais 
to Paris and returned to its place of depar- 
ture, which really was Chalais-Meudon, a 
suburb of Paris. 
A. Lawrence Rotcu * 
BLuE HILL METEOROLOGICAL OBSERVATORY 
SPECIAL ARTICLES 
HEATING OF LOCAL AREAS OF GROUND IN CULEBRA 
CUT, CANAL ZONE” 
THE marl shales, through which Culebra 
Cut extends, in the region opposite the Cule- 
bra railway station, have, from time to time, 
on exposure to the atmosphere, become hot. 
The intensity of this heat has varied from 
noticeably warm to a temperature sufficient 
to readily char wood, without, however, caus- 
ing it to burst into a flame. The duration of 
this heating has been from a few days to sev- 
eral weeks. These shales are dark, thin 
bedded, soft and easily crumbled, and some of 
the layers are largely fine basic tuff, loosely 
cemented by lime. Other beds contain more 
carbonaceous material, with some local part- 
ings of lignite an inch to a foot or more thick. 
The relatively unweathered character of these 
basic sediments is evidence that they were de- 
rived from nearby volcanic mountains, and 
the carbonaceous and lignitic layers in them 
indicate shallow water and swamp conditions 
of deposition. The presence of fossil oysters, 
pelecypods, corals and foraminifera show 
that these shallow estuaries were marine, and 
that they existed in early Tertiary time. Dr. 
T. Wayland Vaughn, of the U. S. Geological 
Survey, examined some of the specimens on 
the ground and gave it as his opinion that 
they are Oligocene in age. The evidence so 
far points to a shallow water connection be- 
tween the Atlantic and the Pacific during 
Oligocene time. 
1 This review was written immediately before the 
lamented death of Professor Rotch.—ED. 
? Published by permission of the chairman of the 
Isthmian Canal Commission. 
SCIENCE 
701 
After exposure to the atmosphere by drill- 
ing, or blasting, certain local areas of this 
formation become, in the course of a few 
days, warmed up, and as the heating goes on 
the carbonaceous matter in the shales is grad- 
ually oxidized off and they tend to assume a 
gray to dull reddish color. The first working 
hypothesis entertained in looking toward a 
solution of this heating phenomenon was that 
possibly the heavy blasting had furnished 
heat enough to break down the calcium car- 
bonate present to the oxide form, and that 
ground water and atmospheric moisture re- 
acted on this to slake it and thus probably 
generate sufficient heat to start the oxidation 
of the carbonaceous material. This hypothe- 
sis was, however, rendered untenable by three 
lines of evidence: 
1. The heating was much more local than 
the calcium carbonate, and the carbonaceous 
matter. 
2. The heating bore no definite relation to 
the lime and carbon content of particular 
beds. 
3. Colonel Gaillard, in charge of the Di- 
vision, informs me that in some instances the 
heat began in the holes some time after they 
had been drilled, but before the ground had 
been blasted at all. 
Another line of inquiry was suggested by 
finding a small amount of pyrite in some of 
the beds which were heating. It was sus- 
pected that this, through its oxidation, was a 
factor in furnishing the initial heat of the 
action. In April, 1911, samples of the beds 
then heating were sent to the chemical labor- 
atory of the U. S. Geological Survey with in- 
structions to make qualitative tests for sul- 
phur and other products that might serve, 
through oxidation, as the mainspring of the 
action. These tests revealed the presence of 
sulphuric acid to the amount of 1.92 per cent., 
also minute erystals of gypsum. This con- 
firmed the hypothesis that pointed to the 
pyrite present as the substance acted on by 
atmospheric oxygen to develop the initial heat. 
The most aggravated case of heating so far 
noted is now going on in Culebra Cut, about 
350 yards north of the foot of the stair at the 
observation tower near Culebra Station. The 
