The Rastrick Notebook

[Page 64] The Rocket has an additional [words struck through] a small Boiler of the figure and dimentions, annexed in the Margin, which is constantly kept full of Water this serves for the Fire Place, the Grate being three feet wide and two feet long, with an Area of Six Square feet which gives 6/10 of a sqr. foot of Fire Grate for each Horse Power. The Surface of this Boiler exposed to the action of the fire is 18 square feet. It is made of Copper and the flat sides are strengthened by distance Pieces and Rivetts at every three Inches in each direction. by this Means a great large fire Surface is obtained and a great strength is given to the [Page 65] Boiler, the principal objection to this construction, is the difficulty of getting at the inside to clean it out. The Sediment and Scurf of from the Water will mostly settle to the Bottom into the narrow part where it is riveted together, but the scurf or calcareous encrustation will affix itself to all parts of the Inside of the Boiler. It is proposed to clear out the sediment by making a small Hole on each side towards the Bottom to get the hand in but as the distance between the Sides of the Boiler is only three Inches, and as there are so many distance