<p>Marine (Scotch) Boiler
</p>
Single ended <a href="https://en.wikipedia.org/wiki/Scotch_marine_boiler" class="extiw" title="en:Scotch marine boiler">Scotch</a> or Marine boilers up to 9' diameter usually have one furnace; from 9 to 12 feet diameter, two furnaces; from 12 to 15 feet diameter three furnaces; and above 15 feet, four furnaces.
<a href="//commons.wikimedia.org/wiki/User:Andy_Dingley" title="User:Andy Dingley">Andy Dingley</a> (scanner)
1905
Scan from <cite class="book" style="font-style:normal">Bentley (1918)      <i> Sketches of Engine and Machine Details</i>, <a href="https://en.wikipedia.org/wiki/en:London" class="extiw" title="w:en:London"><span title="capital and largest city of the United Kingdom">London</span></a>, pp. p. 108  <small></small></cite>