358 Preparation of Composts for Land. 



2. The mode of cure is probably by strengthening those 

 muscles which give tone to the voice. 



3. Hence, in the more oxygenated climate of England, 

 the nightingale has so melodious a strain. 



4. And probably for the same reason this poetic song- 

 ster only croaks in Egypt, into which country it retires in 

 the winter. 



5. Several of my patients have observed a remarkable 

 strength of voice arising after inhaling the vital air. 



6. A decided experiment was made on this subject by a 

 pneumomeler invented by me, by which the capacity of the 

 lungs may be ascertained : trying with this instrument the 

 capacity of the chest of the right hon. Charles James Fox, 

 Mr. Courtenay, Mr. Kemble, sir James Mackintosh, Bryan 

 Edwards, &c., the power of voice was found to be in exact 

 proportion to the quantity of air inhaled, and therefore pro- 

 bably to the oxygenation of the muscles of the larynx. 



7- Mrs. Siddons made the following decided experiment. 

 After inhaling a super-oxygenated air, she stationed a lady 

 in a remote part of the boxes ; and upon the days the vital 

 air was inhaled only, all her lower tones were most distinctly 

 heard, and I notieed myself this remarkable effect. 

 I remain, dear sir, 



sincerely yours, 



Robert John Thornton. 



LVII. Letter from Marc Taerg, Esq. of Bceston, near 

 Shrewsbury, to Mr. Tilloch, on the Preparation of Com- 

 posts for Land, and on the Composition of Potash. 



Sin Becston, September 1S(W. 



XIaving for some time been engaged in making experi- 

 ments to ascertain what composts are most advantageous tor 

 my land, 1 send you this letter for insertion in the Philoso- 

 phical Magazine, hoping that it may be of some use to 

 farmers, and throw light upon a subject which has lately 

 attracted much attention. 



I will not now take up your time by relating the various 



mixtures 



