INVESTIGATIONS OF THE ALBATROSS. 49 



up with salt, very much diminishing the efficiency of the boilers. 

 Rerolling the tubes has only a temporary effect in stopping these 

 leaks. I have fitted wrought-iron ferules in a number of the leaking 

 tubes, but have not found much good resulting from their use. The 

 tube sheets have cracked in about half a dozen places, across the 

 bridges between adjacent tube holes. I can assign no reason for these 

 cracks occurring. 



In May, 1892, by orders of the Treasury Department, we took on 

 board about 170 tons of Seattle (black diamond) coal. The boilers of 

 this vessel are entirely unsuited to burning this coal, and its use was 

 attended by a serious injury to the boilers and machinery. The coal 

 is really a lignite, and, in burning, it evolves large quantities of gas. 

 This gas (if the fires are forced at all) can not burn in the small com- 

 bustion chambers of our boilers. As a consequence, it passes uncon- 

 sumed through the tubes, but, heated above the igniting point, and 

 coming in contact with air in the uptakes and stack, bursts into a fierce 

 flame. This happened repeatedly while using the black diamond coal, 

 and has never occurred with any other coal that has been used during 

 the year I have served on this vessel. The drum, which is an annular 

 cylinder, forming the lower section of stack, became very much over- 

 heated, and all the joints in it were started leaking. The steam in the 

 drum became very much superheated and i)assing to the engines burnt 

 out the packing all around. The steam had such a high temperature 

 that it melted the solder off an expansion joint in the main steam pipe. 

 The coverings of many small steam pij)es were charred and burnt off". 

 The wooden casing around the auxiliary steam pipe in the port coal- 

 bunker caught fire and ignited the surrounding coal. Since the use of 

 this coal the leaking at the tube ends has been much worse. 



The boilers are in much worse condition than is generally the case 

 with boilers that have had a similar length of service. This is due to 

 the abnormal conditions to which they are subjected. One year of such 

 service as that just closed, during which the engines were stopped from 

 full speed ahead 610 times in addition to the number of stops incidental 

 to cruising, is fully equal to two if not three years of ordinary service in 

 destructive effect. 



F c 92 4 



