BtA-BUB 1 
VISCOSITY OF GASES. 
287 
nomenon in wide tubes, of remarkable clearness and full of suggestion, 
I resolved to communicate these without elaborate reductions. 
EXEKIMENTAL RESULTS. 
Transpiration under variable pressure P—p. — I shall introduce these 
results by a number of experiments made at the outset of the present 
investigation, inasmuch as these have a direct bearing on the feasibility 
of the transpiration apparatus for pyrometric purposes. In these ex- 
periments neither Mariotte flask nor lateral rube was employed, so that 
the pressure fell from the initial to the final value at one end of the 
tube, the other being at atmospheric pressure. The helix itself was 
wound in a flat form of large radius so as to lie completely in the zone 
of fusion of the Bunsen burner. For each special part of the table the 
conditions of flow, however complex, are the same, t is the time of 
efflux of the volume F; L and I denote the length of tube and cold 
ends; R is the internal radius. In Table 95 the tempestuous influx of 
mercury into the receiver B was avoided by opening the stop-cock of 
the Mariotte flask until the flow of mercury had ceased, and then open- 
ing the stop- cock of the capillary. 
Table 93. — Transpiration of air under variable pressure. {Burner not chimneyed.) 
[Capillary tube No. 1. i = 37 cm . Z = 8 cm . i?=r0.025 cm . F =580«. = 20°.] 
Time. 
Initial 
pressure. 
Final 
pressure. 
Barome- 
ter. 
Temperature. 
98 ) 
r 
20°. 
459 
I 
I 
Bright red heat (1,000°). 
99 
} 108 
97 
78 { 
20°. 
459 
| 
| 
Bright red heat. 
98 
J 
I 
20°. 
78 
1 
r 
20°. 
323 
Bright red heat. 
78 
} 118 
107 
78 
20°. 
314 
| 
Bright red heat. 
78 
> 
20°. 
189 
i 
r 
Bright red heat.- 
57 
| 
| 
20°. 
187 
)■ 143 
132 
78 < 
Bright red heat. 
55 
. 
| 
20°. 
187 
J 
I 
Bright red heat. 
(011) 
