118 
DRS. W. RAMSAY AND S. YOUNG ON SOME OF 
temperatures will be found. These show that the relative effect of surface condensa¬ 
tion is much more marked at low than at high temperatures. Thus, at about 30 millims. 
pressure the vapour-density calculated at 75° is 9'01 ; at 50°, 9'46 ; at 40°, 9'90 j and 
at 30°, 10'70. An increase of pressure does not appear to raise the apparent vapour- 
density to the same extent as a fall of temperature. This may explain why an 
increase of pressure, at high temperatures, does not influence surface condensation 
appreciably, except very close to the point of condensation. 
In addition to the work of Regnault, that of Fairbairn and Tate on the densities 
of unsaturatecl and saturated steam may be mentioned. As their results were given 
in English units, we think it well to reproduce them here in the same form as has 
been adopted in this paper. It will be seen that the densities of the saturated vapour 
show a gradual rise with increase of temperature, although the results of individual 
experiments are far from regular. 
Fairbairn and Tate, ‘Phil. Trans.,’ 1860, pp. 218, 219. Quoted by Ranktne in 
Fahr. degrees and cubic feet per lb. 
T. ° C. 
T. 0 Abs. 
Volume of 1 gTm. 
Pressure. 
Vapour-density. 
58-20 
331-20 
c.cs. 
8275-3 
millims. 
135-9 
9-15 
68-51 
341-51 
5333-5 
218-9 
9-09 
70-75 
343-75 
4920-2 
240-0 
905 
77-18 
350-18 
3722-6 
316-7 
9-23 
77-49 
350-49 
3715-1 
320-3 
9-15 
79-40 
352-40 
3438-1 
346-0 
9-21 
83-50 
356-50 
3051-0 
406-7 
8-93 
86-83 
359-83 
2623-4 
466-4 
9-14 
92"65 
365-65 
2149-5 
581-1 
9-10 
117-16 
390-16 
943-12 
1361-7 
9-44 
118-23 
391-23 
908-03 
14101 
9-49 
118-45 
'391'45 
892-54 
1419-6 
9-60 
124-16 
397-16 
759-44 
1697-7 
9-57 
128-41 
401-41 
649-24 
1935-4 
9-93 
130-67 
403-67 
635-30 
2070-8 
9-54 
131-77 
404-77 
605-65 
2138-9 
9-71 
134-86 
407-86 
584*44 
2342-6 
9-26 
13405 
407-05 
543-17 
2287-9 
10-18 
137-45 
410-45 
514-98 
2529-8 
9-79 
139-21 
412-21 
497-25 
2655-2 
9-70 
141-80 
414-80 
458-30 
2864'6 
9-82 
144*74 
417-74 
433-12 
3105-1 
9-65 
142-36 
415-36 
449-62 
2901-9 
9-89 
