When Babemba explained that without the king's direct order it would be foolish and unjustifiable to put to death such magicians as we were, Imbozwi spoke for the first time, asking why he called us magicians.
Babemba instanced the wonders of the shining shield that showed pictures.
"Pooh!" said Imbozwi, "does not calm water or polished iron show pictures ?" "But this shield will make fire," said Babemba.

"The white lords say it can burn a man up." "Then let it burn me up," replied Imbozwi with ineffable contempt, "and I will believe that these white men are magicians worthy to be kept alive, and not common slave-traders such as we have often heard of." "Burn him, white lords, and show him that I am right," exclaimed the exasperated Babemba, after which they fell to wrangling.

Evidently they were rivals, and by this time both of them had lost their tempers.
The sun was now very hot, quite sufficiently so to enable us to give Mr.Imbozwi a taste of our magic, which I determined he should have.
Not being certain whether an ordinary mirror would really reflect enough heat to scorch, I drew from my pocket a very powerful burning-glass which I sometimes used for the lighting of fires in order to save matches, and holding the mirror in one hand and the burning-glass in the other, I worked myself into a suitable position for the experiment.
Babemba and the witch-doctor were arguing so fiercely that neither of them seemed to notice what I was doing.

Getting the focus right, I directed the concentrated spark straight on to Imbozwi's greased top-knot, where I knew he would feel nothing, my plan being to char a hole in it.

But as it happened this top-knot was built up round something of a highly inflammable nature, reed or camphor-wood, I expect.