268 



SCIENCE. 



[Vol. II., No. 30. 



its short life is liopecl to give good argument 

 iu favor of prompt and liberal action b}' an- 

 otlier congress, in which, it is believed, there 

 may be a sufficient number of intelligent and 

 patriotic members to carr}^ the measure through 

 without regard to politics. 



Mr. Bond describes the method adopted by 

 Professor Rogers of Cambridge, and himself, 

 to secure for Messrs. Pratt & Whitney of Hart- 

 ford a standard sj'stem of exact measures for 

 use in creating a basis for gauges to be used 

 iu the United States in general machine con- 

 struction. The comparator built bj- the firm, 

 under the advice of tliese gentlemen, is used. 

 Its readings, with its ' B ' microscope, are 

 made from divisions measuring 0.000016 

 inches. The company has now a set of end 

 measures running by sixteenths to four inches, 

 and a complete plant for making them accur- 

 atelj' to within the forty-thousandth of an 

 inch, a magnitude which can be detected by 

 an expert workman. 



Professor Robinson gives the theory of the 

 peculiar form of pumping-engine known as the 

 Worthington engine. This is a Wolff form of 

 compound'engine in its general arrangement, 

 built without fly-wheel and in pairs, and so con- 

 structed that each double engine has its valve- 

 motion operated hy the opposite machine. He 

 shows that, theoreticallj^, the ' tandem ' type of 

 this combination excels all the other possible 

 adjustments of the engine, in its probable 

 efflciencj'. The efiicieuc}' is not modified per- 

 ceptiblj' by the ordinary- slight variations of the 

 exponent of the expansion curve. Numeri- 

 cal results of the use of the formulas are given 

 in tabular form. The paper is illustrated by 

 engravings of the several forms and parts of 

 these engines. 



Dr. Fraley describes the formation, the 

 growth, and the work of the Franklin institute 

 of the state of Pennsylvania. It was organized 

 in 1824, and has been in active operation ever 

 since. It established the first regular draw- 

 ing-school in the United States, and has kept 

 it in successful operation for fifty years. It 

 has occasionally given exhibitions of domestic 

 manufactures and products, has gathered to- 

 gether a great librarj', cabinets of materials, 

 models, and machines, and has for many years 

 regularly published a journal devoted to ap- 

 plied science and the arts. 



Mr. Wolff gives the results of investigations 

 of the efficiency and power of windmills, and 

 presents a table, calculated in the course of 

 his studies of the subject, of the relations be- 

 tween the pressure and the velocity of the 

 wind at various temperatures, — the first in 



which the densitj' and temperature of the at- 

 mosphere are taken into account. 



Professor Thurston occupies nearly' fifty 

 pages in the discussion of the several efficien- 

 cies of the steam-engine, including the total 

 commercial efflcienc}'. Expressions are given 

 bj- which to determine the best proportions of 

 steam-boilers for given costs of boiler and fuel, 

 storage, etc. The best area of heating surface 

 per pound of fuel burned on the grate varies 

 as the square root of the quotient of all annual 

 expenses variable with the cost of fuel, reck- 

 oned per pound of coal and per square foot of 

 grate, bj' the sum of all annual expenses per 

 square foot of heating surface and per square 

 foot of grate, the latter being reckoned only 

 so far as they are dependent on the size of 

 boiler. The efficiency of engine is found to 

 be dependent upon both the ratio of expan- 

 sion, and the method of variation of waste by 

 internal cj'linder condensation with the point 

 of cut-off. Tables are given of the probable 

 best points of cut-off in the various standard 

 types of engines, at various pressures of steam ; 

 and also of the probable minimum weights of 

 steam and of good coal required by such en- 

 gines at various best ratios of expansion. 



The ' efflciencj' of capital ' is found to be 

 dependent upon similar quantities, as well as 

 upon the costs of fuel, attendance, operation, 

 etc. The theory of the efficiencies of the ideal 

 engine with non-conducting cj-linder is given, 

 and both algebraic and graphical methods of 

 solving problems are presented and illustrated. 

 The theory of the efficiencies of real engines is 

 next treated, and the defects of the Rankine 

 system are remedied. The ' general equation 

 of all steam-engine efficiencies ' is given, as 

 deduced bj' Professor Thurston, and a series 

 of problems falling under the general head are 

 treated by the j^roduction of the necessary 

 formulas and by a graphical construction in- 

 volving the use of his newlj' discovered ' curve 

 of efficiency.' One-half of the paper is de- 

 voted to the solution of various important 

 problems arising iu the practice of the engineer 

 and previously unsolved. Tables follow giv- 

 ing the results as applicable to the common 

 forms of steam-engine, and showing the enor- 

 mous differences in economj' and in the best 

 ration of expansion, size of engine, etc., pro- 

 duced bj' the occurrence of cylinder condensa- 

 tion, a form of waste hitherto untreated by- 

 writers on thermodynamics and the theory of 

 the steam-engine. He saj's, " Hy the use 

 of this, or some more exact method, the art 

 of proportioning the steam-engine can be ele- 

 vated to the rank of a branch of the science of 



