Here is a pix of a clump of scale found in a locomotive boiler, this clump is on the right side of the backhead, the door sheet is removed, there is an equaly sized clump of scale on the left side. http://thumb8.webshots.com/t/50/50/1/68/8/498616808lNJnor_th.jpg With any luck this link should take you to the pix?! Robert Yuill