92 
SHORT NOTES ON PROFESSIONAL SUBJECTS. 
The best method to adopt under any circumstances can easily be ascertained by 
estimating the strains on the various ropes and pickets and making dispositions to 
avoid giving too much strain to any part.* 
On a subsequent occasion the triple blocks were attached to the moving weight; 
more power by the tackles was thus gained, and (more men being available) the 
capstan was not used, but the running end of the gyn tackle Was hauled in by men, 
and the weight (a platform) was brought over in a very few minutes. 
* Disregarding friction and the weight of the ropes the strain can easily he found as follows 
when the gun is in any position G. See fig. 2. 
Fig. 2. 
Let AD, BE represent sheers, 
FA, BO back guys, 
AG, GB tackles. 
First, Through G draw GM vertically; make the length GM to represent the weight of the 
gun. 
Through M, draw ML, MN, parallel to BG, AG, respectively. Then, lengths GL, GN, repre¬ 
sent strains on tackles respectively. 
Second, From A along AG, mark off AK, equal to GL. 
Through K draw KD parallel to FA and through D draw DLL parallel to AG. 
Then AIL represents the strain on back guy and pickets, and AD the thrust on sheers. 
In like manner the strain on the other back guy can be estimated. 
From this it is evident that the greater the angle AGB the greater will be the strains on all the 
ropes. 
ERRATUM. 
p. 60, four lines from bottom, for “ 14 lbs. charges,” read “40 lbs. charges.’ 
