If strength of voice is of paramount importance to the speaker, it is also an element which is very susceptible of cultivation. Professor Russell says,--"The fact is familiar to instructors in elocution, that persons commencing practice [in vocal gymnastics] with a very weak and inadequate voice, attain, in a few weeks, a perfect command of the utmost degrees of force." As has already been intimated, the strength of the voice depends directly upon the condition and use of the respiratory organs, including the larynx, and indirectly upon the general health and vigor of the whole physical system. The volume of breath which can be inhaled, and the force with which it can be expelled determine the degree of energy with which vocal sounds are uttered. This fact affords a clear indication of the proper mode of developing the strength of the voice. It is evident that the exercises which have for their object the strengthening of the voice, should also be adapted to develop and perfect the process of breathing. The student should be frequently trained in set exercises in loud exclamations, pronouncing with great force the separate vowel sounds, single words, and whole sentences, and at the same time taking care to bring into vigorous action, all the muscular apparatus of respiration. Shouting, calling, and loud vociferation, in the open air, both while standing, and while walking or running, are, with due caution, effective means of acquiring vigor of utterance. Children when at play are instinctively given to vociferation, which should be permitted, whenever practicable. One of the most remarkable examples of the extent to which the power of voice may be developed, is that of the Rev. Mr. Whitefield, the celebrated itinerant preacher. Having listened to his preaching in the open air, in Philadelphia, on a certain occasion, Dr. Franklin found by computation, that he might well be heard by more than thirty thousand auditors. It is said that the habit of speaking gave to the utterance of Garrick so wonderful an energy, that even his under-key was distinctly audible to ten thousand people. Dr. Porter sums up this matter thus :--"The public speaker needs a powerful voice; the quantity of voice which he can employ, at least can employ with safety, depends on his strength of lungs; and this again depends on a sound state of general health. If he neglects this, all other precautions will be useless."