ORIGIN OP USEFUL INVENTIONS. 



With regard to the invention and improve 

 ment of the attam-engine a story has been told 

 * that an idle boy being employed to stop and 

 open a valve, saw that he could save himself the 

 trouble of attending and watching it, by fixing a 

 plug upon a part of the machine which came to 

 the place at the proper times, in consequence of 

 the general movement.&quot; Whether or not this 

 story has any foundation in truth certain it is, 

 that all the most useful improvements in this 

 engine have been the result of the most elaborate 

 researches and investigations of scientific truths. 

 The first distinct notion of the structure and 

 operation of this powerful machine appears to 

 have been given by the Marquis of Worcester, 

 in 1663, in his &quot; Century of Inventions.&quot; Its 

 subsequent improvements by Savary, Blackey, 

 Newcomen, Beighton and Fitzgerald, were the 

 results of physical knowledge, of mechanical 

 skill, and of the most laborious investigations. 

 Its latest and most important improvements by 



manufactured by the same artist, a telescope whose 

 object-glass is about seven inches diameter, and its 

 focal length twelve feet, which is now in the pos 

 session of Dr. Pearson. The piece of flint-glass of 

 which the concave lens was formed, cost Mr. Tulley 

 about thirty guineas. Unfortunately for science, the 

 ingenious artist (Guinand) is now dead, and it is 

 uncertain whether he has left any particular details 

 of his process behind him. The possibility, how 

 ever, of procuring glass for the construction of very 

 large achromatic telescopes is now put beyond a 

 doubt. 



The unacientinc reader may acquire a general 

 idea of an achromatic object-glass from the follow, 

 ing figure, where A D represents a double unequally 

 convex lens of crown g-kiss, C B a double concave 

 of flint glass, and E F another convex lens of crown- 

 glass. These are placed together in the manner 

 represented in the figure, and form what is called 



an achromatic object-glass, the term achromatic sig 

 nifying free of colour. Sometimes only two lenses, 

 a convex of crown, and a concave of flint-glass are 

 combined for the same purpose. In the case of a 

 single convex glass, the image formed is blended 

 with the prismatic colours which come to foci at 

 different distances from the lens, and consequently 

 produce a comparatively indistinct image, which 

 will not admit of a high magnifying power. But the 

 achromatic lens, forming an image without colour 

 will bear a larger aperture, and a higher magnifying 

 power, than a common refractor of the same length, 

 .-o great is the difference that an achromatic tele 

 scope of Dollond, only three feet ten inches in 

 length, was found to equal, and even excel the 

 famous aerial telescope of Huygens of 123 feet focal 

 length, and the gentlemen present at the trial agreed 

 that &quot; the dwarf was fairly a match for the giant.&quot; 

 1 he principal obstacle to their construction on a 

 large scale, is, the difficulty of procuring large pieces 

 of flint-glass free of veins, and of a proper dispersive 



6 



Mr. James Watt, were owing no less to t 

 scientific knowledge which adorned his mi 

 than to his mechanical ingenuity. He was a 

 man of a truly philosophical mind, eminently 

 conversant in all branches of natural knowledge, 

 and the pupil and intimate friend of Dr. Black, 

 and had attended the lectures of that distin 

 guished philosopher in the university of Glasgow. 

 And he often acknowledged &quot; that his first ideas 

 on this subject were acquired by his attendance 

 on Dr. Black s chymical lectures, and from the 

 consideration of his theory of latent heat, and 

 the expansibility of steam.&quot; We may therefore 

 rest assured, that all the future improvements 

 and new applications of this noble invention will 

 be the result of physical and chymical knowledge 

 combined with mechanical skill ; and conse 

 quently, no artizan can ever expect to be instru 

 mental in bringing the steam-engine to its highest 

 pitch of improvement, and in directing its ener 

 gies to all the purposes to which they may be 

 applied, unless the pursuits of science occupy a 

 considerable share of his attention. 



The first hint of the mariner s compass is 

 generally supposed to have been owing to chance. 

 Some persons may have accidentally observed, 

 that when a small loadstone is suspended in 

 water on a piece of wood or cork, its ends pointed 

 towards the south and north. Such experiments 

 seem to have been applied at first for mere 

 amusement, and to excite astonishment in the 

 minds of the ignorant and illiterate. But it was 

 not till some genius possessed of science and of 

 reflecting powers seized the hint thus given, that 

 it was applied to the important purpose of direct 

 ing the mariner in his course through the path 

 less ocean. And to science we are indebted 

 for the manner of determining the declination of 

 the needle, in all parts of the world, by means 

 of the azimuth compass, and thus rendering it 

 an accurate guid to the navigator in every 

 region through which he moves. The discovery 

 of that peculiar principle termed galvanism, was 

 partly owing to accident. Whilst Galvani, pro 

 fessor of anatomy at Bologna, was one day em 

 ployed in dissecting a frog, in a room where 

 some of his friends were amusing themselves 

 with electrical experiments, one of them having 

 happened to draw a spark from the conductor, at 

 same time that the professor touched one of the 

 nerves of the animal, its whole body was in 

 stantly shaken by a violent convulsion. Having 

 afterwards suspended some frogs from the iron 

 palisades which surrounded his garden, by 

 means of metallic hooks fixed in the spines of 

 their backs, he observed that their muscles con 

 tracted frequently and involuntarily, as if from a 

 shock of electricity. Such facts, preseated to 

 the view of unscientific persons, might hava pro 

 duced nothing more than a gaze of wonder: 

 perhaps supernatural powers might have been 

 resorted to in order to account for the jhen*. 



