38 



NATURE 



\Nov. 8, 1883 



observer draws away the movable part, which readily 

 rolls on a railway. The extremity of the telescope bear- 

 ing the mirror of the objective is thus left uncovered, 

 while the astronomer, ensconced in his fixed part as in 

 his own room, and sheltered from all inclemencies of 

 weather, studies the infinitely great in conditions as com- 

 fortable as those of the naturalist who examines under 

 his microscope the infinitely little. 



Seeing it is but just that those who bear the burden 

 should also enjoy the honour, we again state that the 

 optical part of this instrument has been executed by the 

 Brothers Henry, and the mechanical part by MM. 

 Eichens and Gauthier. 



THE INSTITUTION OF MECHANICAL 

 ENGINEERS 



'X'HE Institution of Mechanical Engineers have held 

 -•■ their autumn meeting this year in Birmingham — a 

 town which for many years was the headquarters of the 

 Society. The returning to their former seat was specially 

 opportune, because the first paper on the list related to 

 one of the greatest of Birmingham worthies, viz. James 

 Watt. The title of the paper was " On the Inventions of 

 James Watt, and his Models preserved at South Kensing- 

 and Handsworth." The author is Mr. Edward A. Cowper, 

 who, from his long connection with engineering both per- 

 sonally and through his father and uncle, is perhaps as 

 well fitted as any man in England to trace out the course 

 of Watt's inventions. This he has endeavoured to do, 

 using as his main guide the numerous models preserved 

 partly at the South Kensington Museum, partly at the 

 Patent Office Museum, and partly at James Watt's house 

 at Handsworth in Birmingham. Some of the models at 

 South Kensington were in danger of falling altogether to 

 pieces from dry rot and decay, but owing to the exertions 

 of Mr. Sandham, the curator of this department, they 

 have, as far as possible, been repaired ; whilst, in addi- 

 tion, a complete set of photographs has been taken, 

 which, even if the models themselves should cease to 

 exist, would preserve their appearance and construction 

 to future ages. 



The sequence of James Watt's inventions with regard 

 to the steam engine is stated at the end of Mr. Cowper's 

 paper as follows : — 



Firstly, in 1769 he made an invention (the separate 

 condenser) which was practically an improvement on the 

 Newcomen engine, the effect of which was to work 

 pumping engines more economically and quickly. 



Secondly, in 178 1 he produced rotative power for 

 driving factories, obtaining it in a manner by having a 

 heavy balance weight to act one way whilst the steam 

 acted the other way ; however, the obtainmg rotative 

 motion by steam was an enormous advantage, far greater 

 in its effect, in the author's opinion, than the improve- 

 ment in the punping engine. 



Thirdly, the crowning invention of 1782 made the 

 steam engine the one useful motive power, by making it 

 double-acting and fit to drive cotton mills, flour mills, and 

 all other machinery requiring regular rotative motion. 



These various stages are illustrated by the models 

 above mentioned. It is indeed doubtful whether there 

 exists at present any model embodying the first idea of 

 the separate condenser ; but there is a most interesting 

 model at South Kensington showing the condensation of 

 steam in a separate surface condenser, composed of a 

 large number of vertical tubes and provided with an air 

 pump. This form of condenser, which in many cases, 

 such as marine engines, has superseded all others, is thus 

 proved to have been invented by James Watt, and not 

 only invented, but brought to a high degree of perfection. 

 The arrangements in this model, according to Mr. Cow- 

 per (than whom there can be no better authority), are in 



points equal to the best modern examples of surface 

 condensation. 



The only model actually exhibited was an engine of the 

 character of Watt's patent of 1771. It is single acting, 

 and has an open-topped cylinder, air pump, and con- 

 denser. There is a heavy bob on the connecting rod, 

 which is used to help the piston up, while the vacuum 

 formed below it causes it to descend on the return stroke, 

 thus obtaining rotative motion. This engine, however, 

 has a crank, and it is known that for many years Watt 

 was afraid to use the crank in his engines, as it was sup- 

 posed to be barred by another patent : it is true that his 

 patent of 1771 shows a crank composed of a pin in a 

 disk, but this is carefully termed " the point of attach- 

 ment of the connecting rod." In practice, however, he 

 used other methods, chiefly the well known sun and 

 planet motion. Of this there are several different 

 forms, which are illustrated by models at South Kensing- 

 ton. There is also a device consisting of a long rack or 

 ladder fixed to the end of the connecting rod and digging 

 into the teeth of a spur wheel on the engine shaft ; the 

 rod being guided by means of rollers running in a guide 

 plate, so as to keep it in gear throughout the revolution. 



Turning now to the 1782 patent, we find what Watt de- 

 scribes as " the new improved engine, the piston of which 

 is pressed forcibly both upwards and downwards by the 

 power of steam," that is to say, the engine is no longer 

 single-acting, but double-acting. Here the chain hitherto 

 used between the piston-rod and beam is replaced by a 

 parallel motion, and the engine takes very much the form 

 which was still common for shop engines within recent 

 years. A good model of such an engine exists in the 

 South Kensington Museum. 



Some variations of this engine, probably made subse- 

 quently, are also illustrated by models, such as the Bull 

 engine, in which the piston-rod passes out through the 

 bottom of the cylinder, and takes hold of a beam placed 

 lower down. 



Still more interesting are Watt's proposals to make use 

 of the expansion of steam for the saving of fuel ; a dia- 

 gram in one of his specifications shows that he fully 

 understood this action, and he gives several methods by 

 which the load upon the piston may be varied so that 

 when the pressure is least it shall have least work to do. 

 One of these is to mount a weight high up above the beam, 

 which would be lifted when starting from either end of 

 the stroke, and fall after passing the centre ; this has 

 been used even in recent times with good results. Several 

 miscellaneous inventions of high interest are also de- 

 scribed ; one of these is the well-known invention of the 

 steam indicator in probably its earliest and rudest form. 

 Another is a counter for telling the revolutions of an 

 engine, of which an actual specimen in good preservation 

 remains in the Patent Office Museum. 



There is also an arangement for obtaining rotary mo- 

 tion in opposite directions out of the same engine by 

 means of two connecting rods starting from a cross-head 

 at one end of the beam, but working opposite ways. 

 Another model shovvs two hammers worked by a single 

 engine, the one lifted from the belly like an ordinary 

 forge hammer, and the other by depressing the tail like 

 a tilt hammer. A yet more curious device is a semi-rotary 

 engine, of which an unfinished model remains in the 

 Watt Room at Heathfield Hall. Here there is a piston 

 fi.xed in a radial line to the shaft, within a large disk or 

 cylinder. Inside this cylinder, at one part, is a fixed 

 support, against which the steam presses each way as it 

 acts against the pist .n, in either one direction or the 

 other. The reciprocating shaft was made to act by a 

 spur wheel on two racks attached to the pump rods. 

 Watt also invented a very simple form of rotary engine, 

 which, as Mr. Cowper states, has probably been rein- 

 vented at least fifty times since 1782, the year of his 

 patent. 



