Abstract
(1) A new type of oil vacuum gauge equipped with a specially designed compressing chamber is devised. (2) Mercury trap can be avoided in this gauge. (3) Due to the small density of oil, lower pressure can be measured. (4) The cylindrical oil reservoir with a piston is a convenient arrangement for changing the height of the oil surface: our reservoir has no need of using an exhausting system as in the case of a mercury reservoir used in some types of McLeo:l gauge, and no fear of driving the liquid into the vacuum tube by the mistreatment of stop-cocks. (5) Owing to the large viscosity of oil, however, it is impossible to use the gauge in the case when the pressure of gas is rapidly changing
