This section is from the book "Cassell's Cyclopaedia Of Mechanics", by Paul N. Hasluck. Also available from Amazon: Cassell's Cyclopaedia Of Mechanics.
The best material for cleaning felt hats of any colour is re-:listilled benzine. After well rubbing this into the hat, give it a good brushing to remove the dirt; grease-spots should be well rubbed with a rag dipped in the liquid. For grey hats, mix a little light magnesia with the liquid and brush out the powder after drying.
 
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