u CONTENTS. 



Hollow whirl formed in a refervoir from which water flows through an horizontal aperture. Theory 

 deduced from the doflrinc of central forces. The vertical feflion of tlie cavity is convex towards 

 the axis. Other phenomena explained. Lateral communications of motion takes place in the air as 

 well as in water. It is the caufe of found in organ pipes and of the increafed power of found through 

 divergent conical pipes. Remarlcahle difference between the fonorous vibrations in a pipe, and 

 thofe which arc propagated in the open air. The contraftion of the ftream iffuing through an 

 orifice in a plate, is not the Newtonian cataraft. The vejocity of the contrafled ftream, is nearly 

 the fame as that of a body falling freely from the furface of the water in the refervoir. Singular 

 form of the contrafted ftream after iffuing through an aperture not of a round figure. 



V. On the mechanical, Fabrication of Lint, and the Manufadlure of Hats. By 



N. L. - - - - - p, 22 



VI. Report and Obfervations on the Art of Hat-making. W. N. p. 2j 



Defcription of the manufadluring proceffes. Enquiry whether this Art tnay profitably be executed by 

 machinery. Circuniftances neceffary to be attended to. 



VII. A popular Account of Experiments which have been made or attempted, 

 for the Purpofe of obtaining an invariable Meafure of Length, from the Dif- 

 ference between the Lengths of the fame Pendulum, when adjufted to mea- 

 fure different known Portions of Time. (W.N.) - P- 29 



The pendulum is itfelf an univerfal meafure, determined from the time of vibration. Praftical dif- 

 ficulties which probably caufed this refearch to be laid afide. Premium direfted to this objeft 

 by the Society for the Encouragement of Arts. Mr. Hatton's projeft for meafuring the difference 

 of the lengths of the fame pendulum adjufted to meafure different portions of time. Subfequent 

 improvements and experiments with this apparatus. By Mr. Whitehurft and Dr. George 

 Fordyce. 



VIII. On the vibration of the Wings of a Fly. By S. R. - p. 35 



Optical phenomenon which proves that the wings of the common fly makes fix hundred vibrations 

 in one fecond. 



IX. An Account of feveral Veins of Sulphate of Strontian, found in the Neigh- 

 bourhood of Briftol, with an Analyfis of the different Varieties. By William 

 Clay field - - - - - P- 3-^ 



Natural hiftory and chemigal analyfis of fulphatej of ftrontian. Experiments on the deleterious 

 properties of barytes. 



X. Letter from Dr. Beddocs refpedling the Difcovery of Sulphate of Strontian, 

 announced at page ^^^, Vol. II. of this Journal - - P- 42 



Remarks on the communication of Dr. Gibbes, apparently claiming the difcovery that the mineral 

 found near Sodbury, in Gloucefterfhire, is fulphate of ftrontian. Other information. 



Scientific News, and Account of Books - - p. 43 



Reftification of ether. Difference of tones produced by the gafes through the fame pipe; Stereotype 

 printing. Account of the new inftitution for mechanical improvements; its conftitation and 

 lift of members. 



MAY. 



