746 
PROFESSOR 0. REYNOLDS ON CERTAIN DIMENSIONAL 
Table VII.—Thermal transpiration of hydrogen by stucco plate No. 1 ('25 inch or 
6 - 3 miHi ms. thick). Temperature of steam, 212° F. or 100° C. ; temperature of 
water, 63° F. or 17° C. 
Mean pressure by vacuum 
Difference of pressure by 
siphon gauge. 
Ratio of 
mean pressure to 
difference of 
pressure. 
Log of 
Log of 
difference of 
gauge. 
May 6. 
July 11. 
mean pressure. 
pressure. 
indies. 
33-00 
millims. 
858-0 
inch. 
inch. 
•1340 
millims. 
3-404 
252 
2-518—1 
3-127—4 
31-00 
7874 
•1366 
3-470 
227 
2-491 
3-135 
29-00 
736-6 
•1396 
3 "546 
207 
2-462 
3145 
28-50 
723-9 
•1408 
3 576 
203 
2-454 
3-149 
•1400 
3"556 
>» 
3-147 
27-00 
685-8 
•1436 
3"647 
188 
2-431 
3-157 
25-30 
642-6 
•1446 
3-672 
174 
2-403 
3-160 
23-75 
603-2 
•1460 
3-708 
162 
2-375 
3-164 
22-00 
558"8 
•1490 
3784 
147 
2-342 
3-173 
20-00 
508-0 
•1530 
3-886 
130 
2-301 
3-185 
19-00 
482-6 
•1540 
3-912 
123 
2-279 
3-187 
18-00 
457-2 
3-912 
116 
2-255 
3-187 
16-70 
4241 
•1542 
3-917 
109 
2-222 
3-188 
16-00 
406"4 
•1532 
3-891 
104 
2-204 
3-185 
15-80 
401-3 
•1532 
103 
2-199 
3-185 
14-90 
378-4 
•1538 
3-906 
94 
2-178 
3-187 
13-35 
339-0 
•1536 
3-901 
87 
2-125 
3-186 
12-50 
317-5 
•1534 
3-896 
81 
2-096 
3-186 
11-55 
393-4 
•1512 
3-840 
76 
2-062 
3T79 
9-80 
248-9 
. . 
■1506 
3-825 
65 
1-991 
3-178 
9-50 
239-7 
•1512 
3-840 
62-5 
1-977 
3-170 
9-00 
228-6 
•1480 
3-759 
60-8 
1-954 
3T75 
8-00 
203-2 
•1470 
3-734 
55 
1-903 
3-167 
6-00 
152-4 
•1320 
3-353 
45 
1-778 
3-120 
3-25 
82-5 
•1046 
2-637 
31 
1-511 
3019 
3-2 
81-3 
. , 
•1020 
2-590 
1-505 
3-008 
2-0 
50-8 
•0760 
1-930 
25 
1-301 
2-880 
1-8 
45-72 
•0760 
23-5 
1-255 
2-880 
1-15 
29-21 
■0500 
1-270 
23 
1-176 
2-698 
0-7 
17-78 
•0330 
•838 
21 
0-845 
2-518 
0-6 
15-24 
•0280 
•711 
0-778 
2-447 
0 4 
10-16 
•0190 
•482 
0-602 
2-278 
0-3 
7-62 
•0158 
•401 
19 
0-477 
2-198 
With the stucco plate the greatest differences of pressure, both in the case of air and 
that of hydrogen, are small, something less than one-fourth the differences previously 
found in the case of the meerschaum plate No. 2 ; but then with the stucco the points 
of maximum difference are well below the pressure of the atmosphere. 
The difference of pressure between the observations is so small, and. the agreement 
of the observations so great, that by merely joining the points plotted to represent the 
observations, very fair curves are formed. 
