CHANGE OF SHAPE OF RECENT COLLIERS. 147 



Another point, although to be expected, is that none of these ships came back 

 to their original shape when docked. 



In connection with the tank top curves, it should be noted that while the deck 

 of the Jason (Table 3, Plate 84) at Station No. 5 went up only 5-16 inch after 

 launching, the tank top immediately below was forced up i^ inches. On the 

 Orion (Table 2, Plate 83), where there was an initial convexity of the tank top, it 

 rose 13-16 inch, while the deck at Station No. 5 rose ^ inch. 



As originally planned on the Neptune, there were no stations for sights aft of 

 the cargo holds. Just before completion it was decided to establish Stations Nos. 

 7 and 8, and readings were taken at the last two sets of observations, but as they 

 did not materially alter the curve, these additional stations were omitted on the 

 later vessels. 



Of these colliers, only the Neptune had expansion joints in the track for hand- 

 ling coal fore and aft, and on her some observations were taken to make sure that 

 the joints allowed sufficient play to relieve the track from undue longitudinal stress. 

 The readings are given on Plate 85, and show that for an increase of sag of about 

 3 inches, there was no motion at all in the joints. The first set of readings was 

 taken without reference to the question of change in shape of the hull, but as the 

 ship was substantially in the same state on May 23 (see Table i, Plate 83) as on 

 June 14, it will be seen that in changing from maximum hog to maximum sag, 

 practically no motion took place in the joints. 



In the case of each of the three ships, the change in shape due to fitting out 

 after launching is obscured by the rising temperature, which produced a hog; 

 while the effect of the former is not clear, some light is thrown on this by the tank 

 top curve in the case of the Orion, which shows that putting in the machinery re- 

 duced the hog of the tank top although, owing to much higher temperature, the hog 

 of the upper deck had been considerably increased. 



As regards change in shape due to temperature alone, none of the observa- 

 tions on either the Orion or the Jason afforded any good comparison. In the case 

 of the latter, there are, it is true, two observations made at different times with the 

 ship complete, but the conditions of loading, etc., as indicated by draughts, show 

 that these cannot properly be compared with one another. This lack of ability to 

 compare the temperature effects is the more regrettable as it was on these two ships 

 that tank top readings were possible. 



On the Neptune, however, two sets of readings were taken on the same day 

 (Table i, Plate 83) and under the same conditions of loading. The ship was very 

 nearly complete, and if tank top readings had been possible, the results would have 

 been even more valuable. These observations show that for a rise of temperature 

 of 7° F. the maximum hogging increased i inch, while the two curves (Table 3, 

 Plate 84) show that the effect was fairly uniform throughout the length of the 

 vessel. 



The method of taking sights was very simple. A transit instrument mounted 

 on a special short-legged stand was placed on a breast hook at the stem head, its 



