THE ROYAL ARTILLERY INSTITUTION. 
483 
THE 
MULTIPLYING ALIDADE, OE PEAGTICE EEGISTEE. 
BY 
MAJOR A. INNES, 
ABERDEENSHIRE ARTILLERY VOLUNTEERS. 
[COMMUNICATED BY LIEUT.-COLONEL C. F. YOUNG, R.A.] 
The multiplying alidade is an optical instrument for recording 
mensural observations, and is constructed on a principle not hitherto 
applied to purposes of gunnery. It is intended to fulfil the following 
requirements:— 
1. That it shall be under the easy management of one person, pivoting 
on the eye of the observer and capable of the most exact and 
instantaneous alignment. 
2. That it shall have the power of multiplying the angular measure¬ 
ment as shall best suit the scale adopted for the register. 
3. That the observations shall be spotted at regular intervals by 
successive perforations of the register, without removal of the eye of the 
observer, or disturbance of the line of collimation of the instrument 
with the target. 
4. That the scale of the alidade, laid down in minute subdivisions, 
shall be capable of affording the most perfect comparative measurement 
of the results of practice, whether individual or in cumulo .* 
5. That it shall possess the properties and be applicable for all the 
purposes of a level and range-finder. 
