440 Abstract Report of Agricultural Discussions. 
ceutical Journal). Another method of preventing the incrustation 
of steam boilers by water containing the sulphate or carbonate tf 
lime or magnesia is to treat the water with hydrate of baryta. This 
remedy has been the subject of one or more patents, but it is objec- 
tionable owing to the poisonous quality of the water so treated. 
But incrustation, though a fertile source of inctmvenience and 
danger, is not the sole or principal cause of boiler explosions. Ac- 
cording to Mr. Amos, explosions generally arise " either from s(;me^ 
fault in the original construction of the boiler or from inattention 
in working." And this opinion is strikingly confirmed by Mr. L. E. 
Fletcher, chief engineer of the " Manchester Association for the 
Prevention of Steam Boiler Explosions," who in his monthly report^ 
dated May 27th in the present year, thus expresses himself: 
" It will be seen that all the above explosions ""of the month] occurred from: 
the most simple causes, and that no mystery whatever need be attached to- 
any of them ; while by suitable constmction of the boilers in the first place, 
and due attention to their state of repair in the second, these explosions would 
in every case have been prevented. 
" I am extremely desirous to keep this practical view of steam-boiler explo- 
sions constantly in sight, since I am persuaded no head will be made against 
them generally as long as their causes are considered to be matters of mystery^ 
and their occurrence one of chance. 
" Very few of the explosions that come imder my notice occur from short- 
ness of water, and I believe that to be a much-abused ide;i, and the number of 
explosions resulting from it to be much exaggerated. It appears to be an 
almost stereotyped verdict at inquests, and, the boiler attendant being fre- 
quently killed, there is seldom any witness to the contrary. 
" I find that by far the most frequent cause of explosion is the insufficiency 
of the boiler for its working pressure, either on account of its original con- 
struction, or state of repair consequent upon use ; while those explosions re- 
sulting either from deficiency of water or from extraordinary or reckless pres- 
sure are comparatively rare. In other words, to ])revcnt misapprehension, I 
find that explosion is more frequently due to weakness of the boiler than to 
excessive pressure of the steam." 
Under these circumstances it is highly satisfactory to know that 
the most simple and efficacious method of testing steam boilers is by 
the application of hydraulic pressure. On this point the remarks of 
Mr. Fletcher are especially valuable. 
"I know no means of ascertaining the sufficiency of the original construc- 
tion of a boiler, or of testing the weakness produced upon it by wear and tear 
— in short, of testing either new or old boilers — equal to the lise of hydraulic 
pressure, and think all steam-users would do well to make systematic use of 
this test once a year. In France, I believe, this plan is rendered compulsory 
by the Government, and it would be well w'ere it generally adopted in this 
country voluntarily. Weak places in the plates may pass undetected, even oni 
careful examination, while some parts maj' be inaccessible and concealed from 
view ; but the hydraulic test is sure to detect and expose them all. Its 
timely application would have saved that most disastrous exj)losion which 
occurred some time since, here in Manchester, at a locomotive establishment 
second to none in the kingdom for its high re[)utation ; and since a defect 
passed unnoticed at such an establishment, where the construction of boilers, 
as well as the quality and strength of plates, may well be supj^osed to hava 
