TRANSACTIONS OF SECTION A. 431 
only by patient study, at leisure, of what has been written. The question may 
not unnaturally be asked, If investigations of this kind can best be followed by 
quiet study in one’s own room, what is the use of bringing them forward in a 
Sectional meeting at all? I believe that good may be done by public mention, in 
a meeting like the present, of even somewhat abstract investigations; but whether 
good is thus done, or the audience merely wearied to no purpose, depends upon the 
judiciousness of the person by whom the investigation is brought forward,’ 
It might be urged that these remarks are as pertinent now as they were forty 
years ago, but I will leave them on their own weighty authority. I will not myself 
venture to emphasise them, lest some of my hearers should be tempted to retort 
that the warning might well be borne in mind, not only in the ordinary pro- 
ceedings of the Section, but in the composition of a Presidential Address ! 
The following Papers were read :— 
1. Thermal Dilatation of Conpressed Hydrogen. 
By A. W. Witkowski. 
The experiments of which the results are quoted below were undertaken with 
the view of obtaining data necessary for the construction of isothermals of 
hydrogen, down to the lowest available temperatures. The immediate object of 
these determinations was the volume-coefficient of dilatation a, as depending on 
pressure and temperature, a being defined by the equation v =v, (1 + 44), in which 
vo and v denote the volumes of any quantity of hydrogen, measured both under a 
constant pressure of p atmospheres, at the temperature of melting ice, and 0 
(Centigrade, constant volume, hydrogen scale) degrees respectively. The method of 
experimenting was similar in principle to that used in the author’s previous 
researches on atmospheric air.1 A summary of the most reliable results, as far as 
they go up to now, is contained in the following table, illustrated by the annexed 
diagram. 
Pressure | Temperature @ 
= +100? | +207 | -77° | ie | tae | —190° 
Values of 10° x a. 
1 36671) — == —_ _ 367-2? 
10 3646 364-7 365-2 365°6 366°8 369-0 
20 362°9 363°2 3640 3649 36771 3719 
30 3611 361°6 362°9 3640 367°2 374:1 
40 359°4 360°2 3618 363°1 367:0 375'8 
50 3576 358°7 360°8 362°1 366°4 377:0 
60 355 8 357°1 — 361'1 3652 3775 
1 Régnault. 
* Travers and Senter (Brit. Assoc. Rep, 1901). 
The last figure is expected to be uncertain, probably by less than five units. 
1 Cracow Acad. Rozpramy, vol. xxiii. 1891. 
