202 
THE NATIONAL GEOGRAPHIC MAGAZINE 
than the single triple flight at Gatiin. The 
Gatun spillway claims approximately a 
quarter of a million yards. 
Nowhere else in the world does one 
get a more vivid impression of the versa- 
tility of concrete than on the Panama 
Canal. They are using it to make the 
giant locks, and with equal success in 
constructing the huge piers and docks at 
the ends of the big waterway. They 
have been trying out a cement gun to 
shoot cement — sand and water, mixed as 
it passes out of the nozzle — against the 
sides of the Culebra Cut, to form a coat- 
ing of solid artificial rock, although the 
experiment has not proved as much of 
a success as had been hoped. They are 
building light-houses and other aids to 
navigation out of concrete, and have 
even gone so far as to build barges of 
this material. 
Nowhere else in the world is there to 
be found such extensive concrete mixing 
plants or such remarkable machinery for 
handling the material. Millions of bar- 
rels of cement had to be carried to the 
Isthmus and millions of yards of stone 
had to be quarried and crushed at Ancon 
and Porto Bello. Sand by the hundreds 
of barge-loads had to be brought from 
islands in the Atlantic and the Pacific to 
keep filled the seemingly insatiable maws 
of dozens of giant mixers, which receive 
some ten tons of sand, cement, crushed 
stone, and water, whirl them around for 
a minute in a sort of digestive process, 
and then dump the mass out in the shape 
of unhardened artificial stone. 
Many new problems in concrete con- 
struction have been worked out at Pan- 
ama. The efl^ect of sea water on con- 
crete, the time of setting for such huge 
masses, and a dozen other matters, upon 
which depended the stability of the locks 
and the integrity of the waterway, had 
to be met. All of them were met in the 
spirit of accepting nothing as proven 
until it was proven by actual physical 
test. 
The world is now in the age of con- 
crete, and the Panama Canal must go 
down into history as the greatest efifort 
man ever has made and perhaps ever 
will make to simulate the processes of 
geologic ages and do in days what nature 
required unreckoned years to accom- 
plish. 
HMLTH CONDITIONS 
Turning now from the engineering 
features of the canal to the other phases 
of the work, we find that here equally 
remarkable conditions prevail. While 
we are building a 40-foot canal in less 
time than it took the French to discover 
that they could not build a 15-foot 
waterway, and are making it a glorious 
success with no greater outlay than it 
required for the French to make the 
most dismal of failures, it is largely 
because extravagance and disease con- 
spired against the French as they never 
did before or since against any people. 
They actually had brought over snow- 
shovels, for what no mortal man know- 
eth, and they also were supplied with 
thousands of torch-lights for the cele- 
bration procession. Fine motor-boats 
were shipped to Culebra in anticipation 
of the day when water would be running 
into the canal. 
But then the French did not know 
about the yellow-fever mosquito. They 
actually made things easier for their tiny 
but most deadly foe. They set the posts 
of their hospital beds in little pans of 
water to keep the ants away — and the 
yellow-fever mosquito reveled in it. 
When we went to Panama we had 
learned the secret that the mosquito had 
kept hidden from humanity for all the 
generations before. If the Spanish- 
American War had taught the necessity 
of the Panama Canal, it also furnished 
the lesson which made the work possi- 
ble. The lessons of sanitation at Ha- 
vana, and the making out of a complete 
case against the yellow-fever mosquito 
by Drs. Reed, Carroll, and Lazear, put 
into practice by so able a sanitarian as 
Dr. Gorgas, at Panama, has served to 
make the Isthmus almost a tropical 
health resort. 
When it is considered that the pro- 
portion of colored population on the 
Isthmus to the white population is larger 
than obtains in any American city, and 
that in spite of this the Canal Zone death 
rate is as small as that of the most 
healthful of American cities, the success 
