Level - Suijunki (English) level

Japanese: 水準器 - すいじゅんき（英語表記）level

A tool for checking horizontality. The most common type uses bubbles, and is called a spirit level. It is made by sealing alcohol or ether in a curved glass tube (a bubble tube) with a large radius of curvature, leaving small bubbles, and fixing the arc upwards on a flat plate. If the top and bottom surfaces of the plate are parallel and the installation is accurate, the bubble will be in the center of the tube when the device is level. If this is set as the zero position and a scale is marked on the tube, small inclinations within the range of the bubble's movement can be measured. There is also a flat-plate-shaped tool that uses a spherical glass container to simultaneously check the inclination direction of the test surface. The direction in which the bubble moves is the direction of the steepest inclination, and the amount of movement indicates the amount of inclination. Alcohol or acetone is used as the liquid because it has a low melting point and does not freeze, and its viscosity is low, making it sensitive to the movement of bubbles. The English word "spirit" means alcohol. In addition to being used in construction and machine installation, there is a precisely made Talcott spirit level as an accessory for astronomical observation and surveying equipment. In addition to the bubble type, there is also the Braun type level, in which a glass funnel is inserted into each end of a long rubber tube, and water is poured into both ends, and the level is measured by the height of the water level on both sides. In the past, in Japan, a tool consisting of a long wooden or bamboo pipe connected at right angles to both ends was used to fill the foundations and beams with water, and the craftsmen who did this were called water-filling carpenters.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

水平を検定する器具。気泡を利用したものが最も一般的で，気泡水準器 spirit levelという。曲率半径の大きい弧状ガラス管 (気泡管) に，小気泡を残してアルコールまたはエーテルを封入密閉したもので，平らな板に弧を上向きに固定して使う。板の上下面が正しく平行，また取付けも正確であれば，器具を水平にしたとき気泡は管の中央にくる。ここを0位置として管に目盛りをつけておけば，気泡の動く範囲内で小さい傾斜は測定できる。検測面の傾斜方向も同時に見るために，球面ガラス容器を使った平盤状の器具もある。気泡の動いた方向が傾斜の高い方向で，動いた量が傾斜の量を示す。液にアルコールやアセトンを使うのは，融点が低く凍らないこと，および粘性が小さく気泡の動きが敏感なためで，英語の spiritはアルコールの意味。建築や機械の設置に使われるほか，天文観測用や測量機用の付属器具として，精密につくられたタルコット水準器がある。気泡式以外では，長いゴム管の両端にガラス漏斗を差込んで水を入れ，両方の水面の高さで水平をみるブラウン式水準器もある。日本でも昔は，長い木樋，または竹管の両端に木管を直角につないだ道具を使い，水を入れて建築土台や梁の水平検定をし，その職人を水盛り大工といった。

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