Lord John is pleased that he hasn't broken her concentration. The last thing he needs is to be shot by an arrow, all things considered.

"It's a remarkable weapon," he observes. "I admit, I've never had the opportunity to train with such a device myself. My father was rather partial to the sword, you see, and a rifle is much more practical on the battlefield." 

Not that he supposes that she was taking her own bow to war precisely. (And not that John's rifle is quite the modern gun either.)