16 Physiology of Speech. 



by long habit and effort, have overcome his impediment ; then 

 let him gradually ^ as he may be able, resume the more usual 

 mode of speaking, by interrupted enunciation. I am persuaded, 

 that this is the principal means employed by those gentlemen who 

 have undertaken to correct impediments in the speech, and it is, 

 undoubtedly, the most rational. In addition to this rule, let the 

 stammerer endeavour to speak in as calm and soft a tone as pos- 

 sible ; for in this way the muscles of speech will be called least 

 forcibly into action, and that action will be least liable to those 

 violent checks or interruptions, in which stammering appears to 

 consist. It would, of course, be irrelevant to the object of this 

 essay, to allude to those other principles connected with stam- 

 mering, such as nervousness, of which it would be necessary to 

 treat, in an essay written expressly on this interesting subject. 



Art. III. On some Cases of the Formation of Ammonia, and 

 on the Means of Testing the Presence of Minute Portions 

 of Nitrogen i?i certain states. By M. Faraday, F.R.S., 

 Corr. Member Royal Acad. Paris, 8fc. S^^c. 



[Communicated by the Author.] 



The importance of the question relative to the simple or com- 

 pound nature of any of the substances considered as elementary in 

 the present state of chemical science, is such as to make any 

 experimental information respecting it acceptable, howe^ver imper- 

 fect it may be. An opinion of this kind has induced me to draw 

 up the following account of experiments relative to the formation 

 of ammonia, by the action of substances apparently including no 

 nitrogen. The experiments are not offered as satisfactory, even 

 to myself, of the production of ammonia without nitrogen ; indeed, 

 I am inclined to believe the results all depend upon the difficulty of 

 excluding that element perfectly, and the extreme delicacy of the 

 test of its presence afforded by the formation of ammonia : yet as, 

 on the contrary, notwithstanding my utmost exertions, I have failed 

 to convince myself that ammonia could not be fonned, except nitro- 



