O74 / 
ing, Dec. 20, the bridge was traversed by two trains, 
advancing side by side from one end, and composed 
of twenty locomotives, and enough cars loaded with 
gravel to together cover both tracks completely. The 
independent span C D was occupied entirely by en- 
gines when the bridge was fully loaded. The deflec- 
tion of the point C under the test was between six 
and seven inches, being an aggregate arising from 
the yielding of A B, the compression of the tower, 
and the deflection of B C itself. On the removal of 
this load, of double the amount which will probably 
ever be imposed upon the structure, the bridge com- 
pletely recovered itself. 
The application of the cantilever in bridge-build- 
ing may be seen in several other instances in this 
country. Sometimes it has been used to diminish 
the opening to be spanned by a single truss, and 
more frequently it has been introduced to facilitate 
the erection of a bridge in places where temporary 
supports in mid-channel could be obtained only with 
great difficulty and expense. A wagon-bridge at 
Fort Snelling, Minn., furnishes an example of the 
former class; but the cantilevers are reduced to simple 
triangular brackets, projecting some thirty or thirty- 
five feet beyond the faces of two adjacent piers, and 
reducing the span to two hundred feet. The Cin- 
cinnati southern railway bridge, over the Kentucky 
River, has three spans of three hundred and seventy- 
five feet each. As the gorge which this structure 
€rosses is two hundred and seventy-five feet deep, 
and ordinary false-works were out of the question, 
the spans were built out from each cliff as projecting 
trusses, anchored back to the rock. By the aid of 
one temporary timber tower on each side, and the 
iron piers, the bridge was thus joined in the middle. 
The lower chord connections were then severed at 
three hundred feet from each bank, leaving the mid- 
dle span with a cantilever of seventy-five feet project- 
ing from each of its ends. Here the introduction 
of hinges obviated the changes of strain which would 
otherwise be caused by the effect on the tall iron piers 
of changes of temperature. The Minnehaha bridge, 
across the Mississippi River, between St. Paul and 
Minneapolis, has three spans, and was erected like 
the Niagara bridge, —the two shore-arms on false- 
works, and the middle span as two cantilevers, which 
are connected by a hinged joint in mid-river, without 
any independent span. 
A design for the Frazer-River bridge on the Cana- 
dian Pacific railway, by Mr. Schneider, although not 
yet erected, antedates the Niagara bridge, and is like 
it, only on asmaller scale. The design for the Black- 
well’s Island bridge, across the East River, New York, 
which was awarded the first prize in 1876, introduced 
cantilevers and an independent span. A similar type 
of bridge is in progress at St. John, N.B.; one is 
proposed for the new Harlem-River bridge, New 
York; and the great bridge for crossing the Frith 
of Forth, now under construction, is a bold design 
of this type, having two openings of seventeen hun- 
dred feet each. Others might be mentioned if space 
permitted. 
CuHas. E. GREENE. 
SCIENCE. 
Bi AS is Veh 
[Vou. III., No. 66. 
THE CHOLERA BACILLUS.1 
THE question, which, in my last report of Jan. 7, 
was left unanswered, — whether the bacilli found in 
the intestines affected with cholera are parasites due 
to cholera alone, — may be looked upon as answered. 
It was at first exceedingly difficult, on account of 
the varying conditions under which the pathological 
changes took place in intestines affected by cholera, 
and on account of the great number of bacteria 
constantly present in them, to find out the bacillus 
proper to the disease. In most cases death occurred, 
not at the height of the cholera process, but dur- 
ing the period of reaction immediately following, 
in which such important changes take place in the 
condition of the intestines and their contents, that 
it is impossible, from such cases alone, to gain a clear 
conception of the cholera process. Only when one 
has had an opportunity to dissect a number of un- 
complicated cases, and to compare with them the 
conditions exhibited in persons when first attacked, 
is it possible to gain a correct insight into the patho- 
logical conditions of cholera. On this account it 
was always kept in view, to use the greatest caution 
in accepting any theory as to the connection of the 
bacterial condition and the cholera, or as. to causal 
connection of the bacteria with cholera, till the full 
proof might be obtained. 
In the last report, I could already state that the 
peculiarities of the cholera bacteria were so well 
determined that they could safely be distinguished 
from others. Of these characteristics, the following 
are the most striking: the bacilli are not perfectly 
straight, like other bacilli, but slightly curved, like a 
comma. The bending may go so far that they take 
the form of a half-circle. In the pure cultivation 
from these bent rods often arise s-formed figures, 
and more or less long, slightly wavy lines, of which 
the first are made up of two, and the last of a large 
number, of the cholera bacilli, which, by continued 
increase, have remained connected. They possess 
powers of locomotion, which can best be seen, and 
in most marked degree, in a drop of cultivation- 
liquid suspended on a cover-glass: in such a prepara- 
tion, one sees the bacilli moving with the greatest 
velocity in all directions through the field. 
Especially characteristic is their action when culti- 
vated in gelatine, in which they form colorless colo- 
nies, which at first are closed, and appear as if they 
consisted of very brilliant little glass particles. 
Gradually these colonies liquefy the gelatine, and 
spread out to a considerable extent. In gelatine cul- 
tivation they are, therefore, through this remarkable 
appearance, very surely distinguished from other 
bacteria colonies, and can easily be isolated from 
them. Moreover, they can pretty surely be dis- 
tinguished by cultivation in hollow slides, as they 
always go to the edge of the drop, and in that posi- 
tion can be recognized by their peculiar movements, 
1 Sixth report of Dr. Kocu of the German cholera commis- — 
sion, dated Calcutta, Feb. 2, 1884. Translated from the Berliner 
klinische wochenschrift for March 31. An abstract of the seventh =a 
report will be found in the Notes and news. 
