respecting Sound and Light. 147 



hypothesis which I once took the liberty of submitting to the 

 Royal Society, on the functions of the crystalline lens, 



I am, &c. 



Emanuel College, Cambridge, THOMAS' YOUNG. 



8th July, 1799. 



EXPLANATION OF THE FIGURES. 



(See Plates III. IV. V. VI. and VII.) 

 Plate III. 



Figs. 1 — 6. The section of a stream of air from a tube .07 

 inch in diameter, as ascertained by measuring the breadth 

 of the impression on the surface of a liquid. The pressure im- 

 pelling the current, was in Fig. 1, 1 inch. Fig. 2, 2. Fig. 3, 

 3. Fig. 4, 4. Fig. 5, 7. Fig. 6, 10, 



Figs. 7 — 12. A similar section, where the tube was .1 in dia- 

 meter, compared with the section as inferred from the experi- 

 ments with two gages, which is represented by a dotted line. 

 From this comparison it appears, that where the velocity of 

 the current was small, its central parts only displaced the 

 liquid ; and that, where it was great, it displaced, on meeting 

 with resistance, a surface somewhat greater than its own sec- 

 tion. The pressure was in Fig. 7, 1. Fig. 8, 2. Fig. 9, 3. Fig. 

 10, 4. Fig. 11, 7. Fig. 12, 10. 



Figs. 13 — 20. A, the half section of a stream of air from a 

 tube .1 in diameter^ as inferred from experiments with two 

 water gages. The pressure was in Fig. 13, .1. Fig. 14, .2. Fig. 

 *5> -5- Fig. 16, 1. Fig. 17, 3. Fig. 18, 5. Fig. 19, 7. Fig. 20, 

 10. The fine lines, marked B, show the result of the observa- 



U 2 



