NEW ELTHAM, LONDON, S.E.9 
49 
Quote Stanley's ‘A’ Catalogue 
THE STANLEY “ENGINEER” 
MEAN-READING LEVEL 
The advantages of the Stanley Mean-Reading Level are immediately 
apparent. They are as follows:— 
(a) Absolutely accurate levels can be taken regardless of any mal 
adjustment in the instrument. 
(b) One operator can test all its adjustments without assistance and 
without even changing his position. 
The two features in the design of this instrument providing these 
attractive facilities are the provision of a revolvable telescope and reversible 
bubble. 
REVOLVABLE TELESCOPE.—This is a provision whereby the 
telescope can be revolved in a mechanical axis through 180° about its axis 
of collimation, thus forming a perfect check on the coincidence of the 
optical axis and the mechanical axis. 
REVERSIBLE BUBBLE.—This is a bubble capable of being rotated 
about its axis without displacement of the air bubble. Such a bubble when 
used in conjunction with the revolvable telescope will determine an 
absolute level plane free from instrument errors and regardless of whether 
the instrument is in correct adjustment or not. 
Briefly perfection of Instrument Adjustment in this Level is achieved 
by exact collimation of the Revolvable Telescope in true parallelism with 
the Reversible Bubble—operations which can be carried out easily in a 
few minutes. 
HORIZONTAL CIRCLE.—Glass horizontal circle is built into the 
Instrument reading by microscope to an accuracy of I minute by estimation. 
This instrument is of the light compact design which has gained so 
much popularity in recent years. It is rapid and convenient in use, and with 
the advantage of being instantaneous checking, makes it a highly attractive 
level for all general purposes, as well as for work of the highest order of 
accuracy.