1380 
Physics. — “On piezo-electric and pyro-electric properties of quartz 
at low temperatures down to that of liquid hydrogen.” By 
H. KAMERLINGH Onnes and Mrs. Anna Beckman. Communication 
N°. 132/ from the Physical Laboratory at Leiden. 
(Communicated in the meeting of February 22, 1913). 
§ 1. Introduction. As many qualities of solid bodies are much sim- 
plified at very low temperatures by the considerable decrease of the 
calorie motion, it seemed desirable to examine also the piezo- and 
pyro-electric effects under these probably favourable circumstances. 
In order to make a preliminary inquiry into this branch of the 
subject we have measured the piezo-electric modulus of quartz, per- 
pendicular to the axis, down to the temperatures of liquid hydrogen. 
Then we have also, at the temperatures of liquid air and liquid 
hydrogen, observed the pyro-electric phenomenon of quartz, which 
FrieDEL, Curir and others have examined at higher temperatures. 
§ 2. Measurements of the piezo-electricity of quartz at low tem- 
peratures. The measurements were effected by the generation of 
electricity on a quartz plate, which was kept at low temperatures 
and compared with a similar plate at ordinary temperature. The 
generated charge was measured with a quadrant electrometer. Both 
the plates were of the same sort as is used in the ordinary Curin’s 
instrument, that is to say, they were cut out of the erystal parallel 
to the optical axis and with the broadest side perpendicular to one 
of the electrical axis. 
e: They were 7—8 cm. long, 2 cm. 
\ broad and 0.06 em. thick. The two 
| + broad, sides were coated with tin *). 
f 
OD 
oy / One of the tin coatings of each plate 
Bc was earthed, the two others were metal- 
g, lically connected with one another and 
a with one pair of quadrants of the elec- 
trometer, as is shown in the figure. 
The other pair of quadrants was earthed. 
All the connections were enclosed in brass tubes, which were in 
1) The tinfoils were apt to get loose from the piate in the liquid oxygen, which gave 
rise to blisters; it would of course be better to employ a platinized quartz plate, 
silvered: Then, too, the use of cementing material between the metal coating and 
the quartz would be obviated. 
