"Note. That the fire capable of flying in the air is of twofold composition, of which the first is: One part of colophon and an equal part of sulphur, two parts of saltpetre, and well pulverized, to be dissolved in linseed or laurel oil. A case, or hollowed wood, is then to be charged with it, and ignited. It will fly suddenly to whatever place you wish, and burn up every thing by its fire."
The second sort of flying fire is prepared in this manner:--
"One pound of sulphur vivum, two pounds of charcoal of linden wood or of willow, six pounds of saltpetre, which three things are minutely pounded in a marble mortar. After that you will charge with it a sheath suitable for flying, or for making thunder.
"Note. The sheath for flying ought to be slender and long, and filled with the aforesaid powder well rammed.
"The sheath for making thunder ought to be short and large, and half filled with the aforesaid powder, and well bound in every direction with an iron band.
"Note. That in every sheath a small aperture is to be made, in order that it may be ignited by the match when applied, which match is made slender at the extremities, but in the middle large and filled with the aforesaid powder."
Another receipt of Marcus for Greek fire is as follows:--
"Greek fire is made in the following manner. Take pure sulphur, tartar, sarcocole, (a kind of resin,) pitch, fused saltpetre, and oil of petroleum. Boil them well together. Dip tow in the mixture, and set fire to it. This fire cannot be extinguished but with vinegar or sand."
The close analogy, or rather the identity, of these compositions with gunpowder as at present made, requires no comment. The more important question is the date at which this work was written. This is a matter of great doubt. Messrs Reinaud and Favé, from the fact that the receipt for the preparation of saltpetre to be found in this same book of Marcus is much more imperfect than that in the Arabian MSS., place the date of his book earlier than the thirteenth century. Again, Geber, an oriental writer, the date of whose life is doubtful, but whom our authors fix at the eighth century, has described the preparation of a salt which has been translated _nitre_, but which our authors consider to have been a sesqui-carbonate of soda, _natron_, not _nitrum_. They thence conclude that nitre was unknown to Geber, and thus, because it was known to Marcus, that he lived subsequently; and for this reason they place Marcus between the ninth and twelfth century.