778 REPORT— 1898. 



adjacent articulations, but with varying degrees of alacrity, as shown in the last 

 lines of the table. Hence this resonance, though essential and very strong, does 

 not differentiate these consonants from each other. Compared with other noises 

 in Nature, they ranked as feebly differentiated hisses ; but our cognition of their 

 differences is sharpened by practice and heredity. A. hiss may be differentiated 

 by (1) the pressure behind it ; (2) the length, width, or roughness of its aperture ; 

 (y) the resonance of the cavity from which (and into which, if any) it proceeds. 

 Diagrams were shown to prove that the difference of h arises from the great length 

 and width of the frictional passage ; that the difl'erence of/ and th arises from the 

 frictional passage of the latter being four times longer than the other, and the 

 pressure greater ; that the rest all differ from these in having some kind of fore- 

 cavit}', which gi'eatly modifies and subdues the frictional noises ; that .s and k/i 

 differ from ch in having strong resonances proceeding from both the fore-cavity and 

 the hinder-cavity, and reinforcing each other; and that s is distinguished chiefly 

 from sh by a second friction, which takes place against the tips of the lower teeth 

 and thus comes unsubdued to the ear. 



4. On the Conservation of Energy in the Human Body. 

 By Edward B. Rosa and W. O. Atwater. 



The total energy taken into the body in the form of food is determined, and 

 balanced against the total output. The experiments continued for a period of four 

 to eight days, and the subject was in one case at rest while in the other he did 

 eight hours of hard work each day. The output of energy consisted of — 



1. Heat radiated from the body and also carried away as latent heat of water 

 vapour given oft' from lungs and skin. 



2. Mechanical work done. 



3. Potential energy of materials contained in excreta and urine. 



The heat was determined by use of the respiration calorimeter briefly described 

 last year before Section A. (The results of experiments were not given then.) 



The food, exhaled air, and excreta are all analysed, and a balance is found for 

 carbon and nitrogen taken in and given off from the body. 



The work done is compared with the total energy received and dissipated, and 

 so the mechanical efficiency of the man as a machine is derived. 



These are the first experiments, so far as we know, which give these results. 

 The apparatus has been developed during six years of active work, involving a large 

 amount of labour and expense, being supported by appropriations from the United 

 States Government. 



5. On a Pneumatic Analogue of the Potentiometer. 

 By W. N. Shaw, F.B.S. 



The apparatus was designed to exhibit two air circuits, having one part of the 

 path of the air common to both, but two separate aiiromotive forces. This 

 arrangement was obtained by having three openings to an otherwise closed box. 

 One of the openings had a sliding shutter, and this formed the common portion 

 of the two circuits. Each of the other openings was provided witli a vertical 

 glass tube, and a small gas jet, either in or below the tube, as tlie case may be ; 

 the hot air thus supplied gave rise to aeromotive forces. By adjusting the sliding 

 shutter the flow in one tube could be made to go in the direction of the aeromo- 

 tive force appropriate to that tube, or in the reverse direction, or could be arrested 

 altogether by adjusting the position of the shutter. In this last-mentioned 

 case, the one aeromotive force is exactly balanced by a fraction of the second and 

 larger aeromotive force by the adjustment of resistances in a manner similar to the 

 balancing of an electromotive force in the compensation method of measuring i 

 electromotive forces. 



The direction of motion of the air in the tubes was identified by a specially 

 designed detector of air-motion consisting of a very light mica flap attached to a 



