142 
pipe on the orifice at the same moment that the lamp was with- 
drawn. The experiments of the first two sets may be regarded 
merely as more exact repetitions of the former ones. Their 
results are confirmatory of those previously obtained. In _ the 
others the flasks were subjected to the temperature of ebullition 
under pressures exceeding that of the atmosphere. Although 
the excess of temperature in no case exceeded two degrees and a 
half, it will be seen that it exercised a decided influence on the 
results. : 
The pressures employed varied from one-tenth of an inch to 
three inches of mercury. According to * Wiillner’s table, founded 
on those of Régnault and Magnus, an excess of 27 63 mill. over 
the normal pressure (760 mill.), determines an increase of 1° C, 
in the temperature of boiling, so that here 0°'924 C. corresponds 
to one inch of pressure. Similarly we have 0”'88 for the second 
inch, and 0°°873 for the third inch. In other words 100°92 C. isthe 
temperature of ebullitionat one inch, 101°*81 at two inches, 102°°68 
at three inches. Indescribing the experiments I use the expres- 
sion “turnip-cheese,” liquid to denote the neutral infusion of turnip 
with cheese of which the preparation has been given above; and in 
recording the results the words barren and pregnant are employed 
to express the absence or presence of living Bacteria. In any 
liquid which has been kept five days at the temperature of fer- 
mentation there is no difficulty in determining in which of these 
two conditions it is, for if Bacteria are present at all they are 
present in such numbers that every field is crowded with them. 
Bodies which appear to be dead Bacteria are met with here and 
there in every specimen. They are as numerous in liquids 
examined immediately after prolonged boiling as in others. 
They are probably derived from the cheese. 
The retorts or flasks were examined after periods varying from 
three to six days, during which they were kept in the warm 
chamber at 32° C. Each was tested by observing that when the 
point of the blow-pipe flame was directed on the neck of the 
flask the softened part was first drawn in and then gave way 
with a loud crack. 
With these preliminary observations I proceed to give an 
account of the experiments. 
March 1.—Two retorts were charged with turnip-cheese liquid 
of which the specific gravity was 1017'2, each retort receiving 
25 c.c. One was immersed in boiling water in a saucepan for 
an hour and then placed in the warm chamber: the other was 
placed in the chamber at once, z7.é. immediately after it was 
boiled and closed hermetically. Both were examined on the 4th. 
The first was barren, the second pregnant. 
March 4.—Nine retorts were charged with cheese-turnip 
liquid, sp. gr. 1020. Each contained 35 c.c. After having been 
boiled and closed hermetically, eight of the retorts were suc- 
cessively subjected in couples to the temperature of boiling water 
in a digester. 
The construction of the digester was such that during the 
ebullition, which in each case was continued for 15 minutes, 
steam escaped through various narrow openings. The heating 
of the retorts was accomplished in four processes, each couple of 
retorts being heated separately and the valve differently weighted 
in different cases. Thus in three ebullitions the weights em- 
ployed were severally 2 lbs., 4 lbs., and 6 lbs., while in the 
fourth, no weight was added to that of the valve itself. The 
experiment was planned in this way in order that the influence 
of pressure might be observed, but in carrying out, it was at 
once observed that with this view the method was a futile one, 
for steam escaped so readily in each experiment through the 
valve that there could be no doubt that all the retorts were in 
reality subjected to the same temperatare, 7.e to the ordinary 
temperature of ebullition. The ninth retort was treated in the 
same way as the others with this exception, that the ebullition 
was continued for an hour, the valve remaining open. 
The liquids were examined March 10. Of the eight which 
were immersed in boiling water for 15 minutes, all were preg- 
nant. The ninth retort was barren. 
March 13.—Six retorts were charged with turnip-cheese 
liquid, sp. gr. ror8, after which they were boiled and closed 
hermetically as before. The retorts were immersed in boiling 
water as previously, but the experiment was so planned that the 
pressure under which ebullition took place could be increased at 
will. The arrangement of the apparatus will be best understood 
from the diagram. A is a strong iron pot (or digester), the lid of 
which fits it by a grooved joint 4, To render the joint air-tight, 
the groove is filled with white lead before fitting on the lid, 
* Wiillner, Lehrbuch der Experimentalphysik, B. IIL., p. 559- 
NATURE 
| Fune 19, 1873 
which is then tightly wedged into its place. The valve 
having been removed, the orifice of the digester is 
stopped. by a vulcanite plug, ¢, through which the long 
tube passes. This forms a perfect joint, for the greater the 
internal pressure, the more tightly it fits. The end of the tube 
dips into mercury contained in a large bottle, ¢, and is retained in 
its place by a holder at d, not shown in the diagram. The 
pot is half filled with water containing a quantity of hay, among 
which the flasks are arranged. It is supported on a triangle and 
heated by a Bunsen’s burner, the mercury bottle being raised on 
blocks until the end of the tube dips to about the right depth 
under the surface of the metal. A more exact adjustment is 
attained by means of the holder already mentioned. 
In this apparatus the six retorts were subjected to the tem- 
perature of ebullition under various pressures, viz., twoundera 
pressure of three inches, two under a pressure of four inches, 
and two undera pressure of two inches. The period of heating 
in each case was fifteen minutes. All of the flasks were placed, 
after heating, in the warm chamber at 32° C., and were examined 
March 18. All were barren. 
March 22.—Four retorts were charged with turnip-cheese 
liquid, sp. gr. 1019, each receiving 50 c.c. Of these two were 
heated in the apparatus at the temperature of ebullition under a 
pressure of one inch, the other two under a pressure of half an 
inch, Of each couple one was accidentally broken. Both the 
remaining ones were examined March 27, and found to be 
barren. 
May 7.—Nine flasks were charged with turnip-cheese liquid, 
sp. gr. 1019, each flask containing 50 c.c. Of these, four were 
subjected to the temperature of water boiling under pressure of 
one inch of mercury for thirty minutes, and four for the same 
period to the temperature of ebullition under one-tenth of an 
inch. They were examined May 12, Of each set one con- 
tained Bacteria, the rest being barren. The liquid in the other 
flask, which was simply boiled, and closed while boiling, had an 
offensive smell, and contained much scum. 
May 22.—Thirteen flasks were charged with turnip-cheese 
liquid, sp. gr. 1019°5. Of these six were subjected to the tempe- 
rature of ebullition at three inches, and six to the ordinary tem- 
parature of boiling water, The remaining flask, after having 
been closed hermetically in ebullition in the same way as the 
rest, was placed with them in the warm chamber. All the flasks 
were examined May 26. All the six flasks of the first set were 
barren. Of the six flasks of the second set four were barren, 
the others contained innumerable living Bacteria. The liquid in 
the other flask was offensive, and contained masses of bac- 
terial scum. 
After the examination several of the flasks containing barren 
liquids, particularly those which had been heated under pres- 
sure, were replaced in the warm ‘chamber. Some of them were 
simply closed hermetically (the liquid having been taken for ex- 
amination by means of a freshly drawn out capillary tube), 
others were closed after the introduction of a drop of distilled 
water. On opening these flasks several days afterwards, it was 
found that those which had been impregnated by the addition of 
