let him stand a half-minute with his head free, and begin again.
When he is submissive, and pleased with you, he will almost always show it by gently champing his bit; but do not be deceived by a nervous simulation which you will probably detect, and which consists in opening the mouth a very little and immediately gripping the bit again. You will have been completely successful when, by simply drawing on the curb-reins, the head is brought to the proper perpendicular position, and the bit, instead of being gripped, is held lightly in the mouth, or, to use the school term, when the horse is "light in hand."
This is the only lesson in the series in which it is possible (though not probable) that your unaided strength may be insufficient; if so, get some one to help you over the first resistance of the horse. With care and tact, however, you will in all probability require no assistance.