PKOPERTIES OF MATTER IN THE GASEOUS STATE. 
745 
Stucco plate No. 1. 
23. As it appeared from Law V., Art. 9, that any increase in the coarseness of the plate 
should reduce the pressure at which the difference should be a maximum for each gas, 
a plate of stucco was tried with this object. 
It was clear that the differences would be much smaller with the stucco than with 
the meerschaum. Therefore this plate was not tried until the differential gauge had 
been furnished with the cathetometer to read to Ttroouth of an inch (^nyth of a 
millim.). 
Final experiments. 
A series of experiments, commencing with stucco plate No. 1, but continued with 
meerschaum plate No. 3 and stucco No. 2, were commenced on May 6, and repeated 
in July. To give all the observations made in this series of experiments would occupy 
too much space, therefore a selection has been made, those results being chosen which 
appeared to be least subject to disturbance. However, the results all agree so well 
that there was but little choice, and it was clearly unnecessary to resort to the usual 
method of taking mean values. Such differences as do exist are sufficiently accounted 
for by the small differences in the temperature of the water, which was several degrees 
higher in July than in May. 
Table YI. —Thermal transpiration of air by stucco plate No. 1 ('25 inch or 6'3 millims. 
thick). Temperature of steam, 212° F. or 100° C. ; temperature of water, 65° F. 
or 18°-4 C. 
Mean pressure by vacuum 
gauge. 
Difference of pressure by 
siphon gauge, July 11. 
Ratio of mean 
pressure to 
difference of pressure. 
Log of 
mean pressure. 
Log of 
difference of 
pressure. 
inches. 
29-80 
millims. 
756 - 9 
inch. 
•0220 
millims. 
•559 
1360 
2-474-1 
2-342-4 
28-50 
723-9 
•0225 
•571 
2-455 
2-352 
25-85 
656"6 
•0235 
•597 
2-412 
2-371 
23-40 
594-4 
■0250 
•635 
903 
2-369 
2-397 
22-20 
563-9 
•0266 
*675 
835 
2-346 
2-424 
17-40 
443-9 
•0294 
•746 
2-240 
2-468 
15-40 
391-2 
•0336 
•813 
2-187 
2 - 526 
13-60 
345-4 
•0342 
•868 
2-133 
2-534 
12-25 
311-1 
•0348 
•884 
2-066 
2-541 
11-35 
288-3 
326 
2-053 
2-541 
10-00 
254-0 
•0366 
•929 
2-000 
2-563 
9-00 
228-6 
•0380 
•965 
1-954 
2-579 
7-50 
190-5 
i ? 
200 
1-875 
2-579 
6 - 75 
171-4 
•0376 
•955 
1-630 
2-575 
6-00 
152-4 
•955 
1-778 
2-575 
5-15 
130-8 
•0362 
■917 
142 
1-711 
2-559 
4-35 
110-5 
■0354 
■899 
120 
1-638 
2-549 
3-50 
88-9 
•0306 
•828 
107 
1-544 
2-513 
2-90 
73-7 
•0314 
■797 
92 
1-462 
2-496 
2-35 
59-7 
•0290 
•736 
81 
1-370 
2-462 
2-25 
57-15 
•0284 
•721 
79 
1-350 
2-453 
1-25 
31-75 
•0230 
•584 
54 
1-097 
2-361 
0-60 
15-24 
■0149 
■378 
42 
1-778 
2-258 
0-25 
6-35 
•0080 
•203 
31 
1-398 
1-903 
0-15 
2-66 
•0066 
•167 
23 
1-176 
1-819 
5 c 2 
