Linnccan Society. 61 



June 5th. — A paper was read, entitled " Description of a Sound- 

 ing-Board in Attercliffe Church, near Sheffield." — By the Rev. John 

 Blackburn, minister of Attercliffe. 



The church of Attercliffe had long been remarkable for the diffi- 

 culty and the indistinctness with which the voice from the pulpit was 

 heard : these defects have been completely remedied by the erection 

 of a concave sounding-board, having the form resulting from half a 

 revolution of one branch of a parabola on its axis. It is made of 

 pine-wood ; its axis is inclined forwards to the plane of the floor at 

 an angle of about 10 or 15°; it is elevated, so that the speaker's 

 mouth may be in the focus j and a small curvilinear portion is re- 

 moved on each side from beneath, so that the view of the preacher 

 from the side galleries may not be intercepted. A curtain is sus- 

 pended from the lower edge, for about' eighteen inches on each side. 

 The effect of this sounding-board has been to increase the volume of 

 the sound to nearly five times what it was before ; so that the voice 

 is now audible, with perfect distinctness, even in the remotest part of 

 the church j and more especially in those places, however distant 

 they may be, which are situated in the prolongation of the axis of the 

 paraboloid. But the side galleries are also benefited, probably from 

 the increase of the secondary vibrations excited in a lateral direction. 

 Several experiments are related illustrative of these effects • among 

 which the most striking was one in which a person placed so as to 

 have one ear in the focus of the paraboloid, and the other towards a 

 person speaking from the remote end of the church, heard the voice in 

 a direction the reverse of that from which it really proceeded. The 

 superior distinctness of sounds proceeding from the focus, is ac- 

 counted for by their all arriving at the same moment of time, at a 

 plane perpendicular to the axis, after reflection from the surface of the 

 paraboloid j which is a consequence of the equality of the paths 

 which they have described. 



LTNN^AN SOCIETY. 



June 17. — A paper was read, entitled, " Description of a species 

 of Tringa killed in Cambridgeshire, new to England and Europe," by 

 Wm. Yarrell, Esq. F.L.S. 



The author describes a singularly marked Tringa, which was shot 

 in Cambridgeshire in the month of September 1826. 



This bird is rendered more than usually interesting from the cir- 

 cumstance that it is not only new to this country, but is acknow- 

 ledged by the best practical ornithologists of the day, to be also en- 

 tirely new to Europe. It is described by Monsieur Vieillot, under 

 the name of Tringa rufescens, as having been found in Louisiana j 

 and a single specimen deposited in the Paris Museum has furnished 

 the only records known. 



A description of the plumage, and the measurement of various 

 parts, are given in detail ; and the paper concludes with a list of the 

 more recent additions to British ornithology, accompanied by refer- 

 ences to the various authorities from whom the first notices of these 

 addenda have emanated. 



ASTRONOMICAL 



