xll CONTENTS. 



II. RemarkaWc Effc(ft of Terreftrial Refradion on a diftant Headland.— Ex- 

 trad of a Letter from Andrew EUicot to David Rittenhoufe, Efq. dated at 

 Pitifljurg, Not. 5, 1787, concerning Obfervations made at Lake Erie p. 152 



Phenomenon called Looming. Prefqu* Iflc feen double, with frequent and fingular changes. 



III. Extraft of a Memoir of Mr. Benedicfl Provoft, of Geneva, on the Emana- 

 tions of Odorant Bodies. B\' Citizen Fourcioy — — P« '53 



FaQe fuppofcd to depend on odorant effluvia. Motions of camphor upon water. Inferences tend- 

 ing to ellablilh a theorj-. 



IV. A Method of Meafuring the Force of an Eleflric Battery during the 

 Time of its being charged. By Lieutenant Colonel Haldane — P- 15^ 



The charge meafiired by the number of explofions of a jar conneiSed with the external furtace of a 

 battery. Experiments. 



V. On the Mechanical ConftriKHion and Ufes of the Screw — p. 15S 



Short defcrlption and theory of the fcrcw. Computation of its effcft. Lofs by friftion. Scientific 

 ufe for meafui ing lines or fpacts. How far it maybe relied on. Account of the method of 

 making fcrews — hy hand — by the tap and fcrcw-tool — and dies. Principal fourccs of error in 

 tapping: — 1. Wave from chaiijje of hands — 2. Drunk ftom prefTure downwards — 3. Undulation 

 from the firft aftion of the dies — 4. Bad fitting or unequal tiardnefs of material — 5. Stttinjj up 

 of the dies not being in the plane of the thread ; and 6. Their cutting on one fide only caufcs 

 irregular depths and crookednefs — 7. Uncertain effetls, by an aftion of the nature of wire- 

 drawing, A fcrew of forty threads in the inch will meafiire to greater precifion than the hun- 

 dred thoufaadth part of an inch. Stock with four pair of dies. Its advantages. 



VI. The Method of obtaining the Fixed Alkalis in CryftaJs of the grcateft 

 Purity. By Lowitz, Profeiibr, &c. at Peterfburg — •— p. 164 



Defcription of the proccfs, with numerous obfervations. Solution in alcohol does not afford pure 

 alkali. 



VII. Experiments on Eaii de Luce. By a Correfpondent — p. 166 



Trial of various fubftanccs. 



VIII. An Account of Experiments defcribed, and in part repeated, at the 

 Sitting of the National Inftiiute of France on the 15th Germinal, in the 

 Year 4. By Citizens Fourcroy and Vaiiquelin — On Detonations produced 

 by Concufiion — — — — — p. :68 



Detonations afforded by the fuper-oxygenated muriate of pot-a(h mixed — with fulpliui — with fnl- 

 phur and charcoal — crude antimony, zinc, metallic antimony, fulphuret of iron, cinnabar, fugar, 

 gum, oil, alcohol, ether. 



IX. A Memoir on the Combination of Oils with Earths, Volatile Alkali, and 

 Metallic Subftances. By M. Berthollet — — P- 17° 



Combinations of fat oil with lime^with ammoniac — with magnefia — with clay— with barytes — with 

 mercury, zinc, tin, iron, copper, lead, filvcr, gold, magnefia, volatile oils, and copper. Ge- 

 neral facts und remarks. 



X. Analylis 



