TRANSACTIONS OF THE SECTIONS. 75 



fi'eys, published in Sowerby's ' Malacological Magazine' (No. 2, 18391. Mr. Jeffreys 

 obtained " Terebratula aurita* plentifully in about 15 fathoms water," and along 

 with it found " Crania personata not uncommon." He procured also the three species 

 of Lima — L. tenera, L. fragilis, L. subauriculata — taken off Sana Island. Nucula 

 minuta was dredged at Oban as well as off the Mull of Galloway ; it has been procured 

 on different occasions by deep dredging in Belfast Bay, and many years ago was found 

 at the Giant's Causeway. The Myrtea spiniferu, of which a single valve was brought 

 up off the Mull of Galloway, was found to be not uncommon in deep water at Oban — 

 on the strand at Red Bay, county of Antrim, I found an example of this shell. Trochus 

 papillosus and Eulima polita, dredged by Capt. Beechey, were not procured at the 

 more northern localities, Sana Island f and Oban — of the latter species, a single living 

 example was taken in the course of the Ordnance Survey in Belfast Bay. The most 

 northern locality on the Irish coast, in, which it had hitherto been obtained, was Dublin 



Bay- 

 Many observations are suggested by these catalogues, and others of a similar nature 



in my possession, but to my friend Mr. E. Forbes must be left the treatment of a sub- 

 ject in which he of all men possesses the most ample and important data. 



MEDICAL SCIENCE. 



On the Construction and Application of Instruments used in Auscultation. 



By C. J. B. Williams, M.D., F.R.S., Professor of Medicine in University 



College, London. 



The acoustic examination of the chest having been so profoundly as well as gene- 

 rally studied, it is not surprising that the instruments used in it should have needed 

 modifications to make them exhibit better the phenomena which increased experience 

 and skill have discovered. To make these improvements, some knowledge of acou- 

 stic science is necessary ; and it might seem to be the province rather of the natural 

 philosopher than of the physician to suggest them. But it must be borne in mind, 

 that a good knowledge of the ends in view, as well as of the instrument, is required. 

 To suggest what a stethoscope ought to be, a knowledge of acoustics is not more 

 necessary than an acquaintance with disease and experience in its investigation. A 

 want of these latter qualifications, in my opinion, renders some recent suggestions 

 of the Professor of Natural Philosophy at Edinburgh of little value to practical men. 

 An imperfect acquaintance with all the purposes and ends of the stethoscope seems 

 to me also apparent in other late proposals for its improvement. 



I now beg to offer a few remarks on the acoustic principle of the stethoscope, and 

 on the best mode of applying this principle to obtain an efficient and convenient in- 

 strument for auscultation. 



Laennec, the inventor, had no accurate views with regard to the principles of the 

 construction of the, stethoscope. He declared that the instruments which he found 

 to be the best Were not constructed according to the commonly received laws of 

 natural philosophy. Experiment taught him that the solid cylinder does not convey 

 the sound of the. breath or voice so well as the cylinder perforated or excavated at its 

 pectoral end. Many years ago I pointed out that this fact, which is unquestion- 

 able, is in perfect accordance with a law of acoustics, that sounds are best conducted 

 by bodies of an elasticity or tension resembling that of the sonorous body. On the 

 other hand, bodies differing in elasticity become bad recipients of each other's vibra- 

 tions. Thus wood, although an excellent conductor of sounds generated in itself or 

 in other solids, receives but imperfectly those produced in air. But by thinning wood, 

 and bringing a large surface in contact with air, it is more readily affected by the 

 vibrations of air, and becomes an excellent medium for transferring to air sounds of 

 denser solids ; and this is the principle of sounding-boards of musical instruments. 



* This species was dredged in Belfast Bay by the collectors attached to the Ordnance 

 Survey. 



t In June 1842, Mr. Hyndman dredged a full-grown Trochus papillosus near Sana 

 Island. 



