PLOTTING QUADRANT, LEVEL, AND CALCULATOR, «i]g, 



^recedhit^ is the cubital cell, which is commonly divided into 

 two, three, or lour. 



All these cells exhibit a g-eat many differences : thus they 

 are iiicouipieie, appea liculdte,'petiolate, &c. These difFer- 

 encCv-i coiist.tute the. characters. 



Tt e whole of the hyraenoptera with which Mr. Jurfne is DiYided into » 

 ^aoquuinted, and his own collection contains 2200 species, he gg^gg^^^* *'^* 

 .inciu<ie:> in i^iS j^ejiera, which he arranges in three suborders, 

 didti li^uisiied b the manner in which the abdomen is at- 

 jtac ed. The vdiptera, arranged according to the i^ame me- Thediptcri 

 thoa, w 11 siiortly appear. promised. 



IX. 



Description and Manner of Using Mr, Robert Salmon's 

 Gf'ometrical Plotting Quadrant^ J^evely and Calculator, for 

 the Use of JSavigatiun and Land~Survei/ing; ascertaining 

 inac essible JJistances, aud Demonstrating and JJetermin" 

 ing vuriou» Problems in Geomtiry and Trigonometry*, 



N the instrument and parts thereof are engraved the Terms used. 

 names given by the inventor, and made use of in these ex- 

 planations; the base line being that at right angles with the 

 90 degrees on the arch, as it is also to the perpendicular, 

 which perpendicular always moves parallel to thejJO degrees. 

 -For the use of land-surveying, where the instrument can be 

 made stationary, the sight (mai'ked a. Fig, 1, P/. V.) with 

 the small hole in it, must be applied; but for sei c?rvicc, 

 the one h, Pig. 2, with the mirror, must be substituted in its 

 place. 



Every person who has iiad occasion to rlescribe or calculate ^^^t ri<Tlit-rme<l 

 the parts of the right-lined figures used in geometry, per- ^^g^ire; resoWa- 



. ,• V IT 1 ., n ble into ttiaii- 



spective, surveymg, navigation, dmlhn^, architecture, &c., ^\^^^ 



murft have perceived, that all of them are resolvable into the 

 most simple of figures, a triangle, or some number of them. 



Hence the great importance of geometry and trigono- Useoftrlgono- 

 iuetry. 

 • The Sftciety of Arts voted Mr. Sahiioii their silver medal and ten 

 guineas for this invention. See thj.r Tratxs-. Tol XXllI, p. 290, whence 

 Vn IS article is extracted. 



' metry 



