TRANSACTIONS OF SECTION G. 567 
3. Experimental Investigation of the Transmission of Heat.* 
By Dr. C. N. Lauper and Professor Petave., F.R.S. 
4. Some New Gyroscope Apparatus. 
By Dr. J. G. Gray and G. Burnsipr. 
TURSDAY, SEPTEMBER 10. 
The following Papers were read :— 
1. Experiments on ‘ Suction’ or Interaction between passing Vessels. 
By Professor A. H. Gipson, D.Sc., and.J. Hannay Tompson, 
M.Sc., M.Inst.C.H. 
In view of the general lack of experimental data as to the magnitude of the 
mutual forces involved in the cases of interaction between two vessels moving 
in parallel paths in close proximity, and as to their effective range of action, the 
authors decided to carry out a series of experiments to investigate these points 
on boats of sufficiently large size to enable the results to be applied with some 
confidence to seagoing vessels. The vessels used were the steam-yacht ‘ Princess 
Louise’ and a motor-boat. Each is propelled by a single screw, and their details 
are as follow :— 
= Length between : Displace- |. Rudder 
Vessel Perpendiculars Beam Draught ment Area 
Ft. In. Ft. In. 
* Princess Louise’ 88 6 13 0 | 6 ft. forward — — 
7 ft. aft : 
| Motor-boat . . 29 6 6 9 |2 ft. 3 in. — 100 sq. in. 
ie 
Two sets of experiments were carried out. In the first the helm of the 
motor-boat was lashed amidships, with the vessels on parallel paths, and its 
behaviour was noted when at different lateral distances, and when the boats were 
moving at different absolute and relative speeds. Its position relative to the 
‘Princess Louise’ was determined by angular measurements taken from the latter 
vessel at intervals of fifteen seconds. Pressures at a series of corresponding 
points on the two sides of the motor-boat were measured at the same instants, 
with a view to determining the lateral forces involved. 
The second series of experiments was devoted to a determination of the helm 
angle necessary to maintain the course of the motor-boat when in different 
positions relative to the larger vessel. 
Owing to possible collision risks the maximum speed was limited to six knots, 
which, in the case of the ‘Princess Louise, corresponds to eighteen knots in a 
vessel of the size of the ‘Olympic.’ The results show that with both vessels 
moving at about this speed with helms amidships the smaller vessel is drawn 
into collision from any lateral distance less than a hundred feet (three and a half 
lengths of the smaller vessel). The precise behaviour depends largely on the 
relative and absoMite speeds of the vessels and on their initial distance apart 
and initial relative position. These points were discussed in the paper, as was 
the question of the helm angle required to prevent collision. 
The authors are of opinion that the experiments prove conclusively that the 
forces involved during interaction are much greater than has been generally 
realised hitherto, while they have been particularly impressed by the rapidity 
with which collision usually follows the first sign of any interaction. 
* See The Hlectrical Review, October 4, 1912, 
