GENERAL UTILITY OF SCIENCE. 



77 



the art of kindling a fire, and of stirring it when 

 kindled, depends on philosophical principles. 

 For example, the stirring of a fire is of use, be 

 cause it makes a hollow, where the air being 

 rarefied by the adjacent heat, the surrounding 

 air rushes into the partial vacuum, and impart 

 ing its oxygen, gives life to the fire and carries 

 the flame along with it. On this principle the 

 following rules are founded. 1. Never stir a 

 fire when fresh coals are laid on, particularly 

 when they are very small, because they imme 

 diately fall into the vacuum, and prevent the 

 access of the oxygen of the atmosphere, which 

 is the principle of combustion. 2. Always keep 

 the bottom bar clear, because it is there chiefly 

 (hat the air rushes in to nourish the fuel. 3. 

 Never begin to stir at top, unless when the 

 bottom is quite clear, and the top only wants 

 breaking, otherwise the unkindled fuel may be 

 pressed down in a body to the bottom, and the 

 access of atmospheric air prevented. 



Illustrations, of a similar kind, of the practical 

 applications of science, might have been given 

 to an almost indefinite extent ; but the above spe 

 cimens may suffice as corroborative of the gene 

 ral position that scientific knowledge would 

 render mechanics and manufacturers of all de 

 scriptions more skilful in the prosecution of their 

 respective employments. 



Some, however, may be disposed to insinuate, 

 that it is quite enough for philosophers to ascer 

 tain principles, and to lay down rules founded 

 upon them, for the direction of the mechanic or 

 artizan ; or, that it is only requisite that the 

 directors and superintendents of chymical pro 

 cesses and mechanical operations, should be 

 acquainted with that portion of science which is 

 necessary for their peculiar departments. But 

 it is easy to perceive, that a mechanic who 

 works merely by rules, without knowing the 

 foundation or reasons of them, is only like a 

 child who repeats his catechism by rote, without 

 attaching a single idea to the words he utters, or 

 like ahorse driving a thrashing machine, without 

 deviating from the narrow circle to which he is 

 necessarily confined. When any accident oc 

 curs, when the circumstances of the case are 

 somewhat changed, when the same principle on 

 which he generally proceeds requires to be ap 

 plied to a new object or mode of operation, he 

 either blunders his work, or feels himself utterly 

 at a loss how to proceed. The least deviation 

 from his accustomed trammels puts him out, 

 because he has no clear and comprehensive 

 view of the principles on which his practice 

 depends. Hence we uniformly find, that a man 

 of scientific acquirements will easily comprehend 

 the plan of any new machine or architectural 

 operation, and be able to execute it, while he 

 who works only by square and rule, will hesitate 

 at eviry step, and perceive innumeraole difficul 

 ties / his way. To confine artists to mere 



rules, without a knowledge of the principles on 

 which they are founded, is to degrade their 

 intellectual nature, to reduce them to something 

 like mere machines, to render them less useful 

 both to themselves and to their employers, and 

 to prevent the improvement of the liberal and 

 mechanical arts. 



The following instance may be stated as a 

 specimen of the advantages of chymical know 

 ledge, and of the practical purposes to which it 

 may be applied in different regions of the globe. 

 A young Parisian, of the name of Leger went 

 on a commercial adventure to Egypt in the year 

 1822 ; but during some of the convulsions of that 

 unsettled country, he lost the little property with 

 which he was intrusted, and was forced to make 

 a precipitate retreat from Suez to Alexandria. 

 He remained some time at Alexandria, destitute 

 and almost hopeless. But the talent of observa 

 tion, and the social habits characteristic of his 

 countrymen, came to his aid : in a lucky mo 

 ment he formed the resolution of retrieving his 

 fortune by introducing the luxury of ice into the 

 parched land of the Ptolemies. This common pro 

 duct of wintry regions is known to be as grateful to 

 the languid natives of tropical climates as ardent 

 spirits are to the benumbed inhabitants of the 

 Polar circle. Having succeeded in effecting a 

 return to his family, the enterprising Parisian 

 was enabled by the friendly assistance of Gay 

 Lussac and Thenard, to adopt the best means 

 that chyrnistry could devise for the preservation 

 of ice, both during the voyage, and after its ar 

 rival in a sultry latitude ; and at length set out 

 from Paris with his inventions, and arrived safely 

 at Alexandria, in April 1823. The sovereign 

 of Egypt, Mahommed AH, was delighted at this 

 novel addition to oriental luxuries ; and, besides 

 valuable presents, gave the inventor the exclu 

 sive right for five years of importing ice into his 

 dominions. This privilege is estimated to be 

 worth one million of francs, or nearly 50,000/. 

 In ancient times the world was enlightened by 

 the learning of Egypt ; the greatest philosophers 

 travelled thither, as to the fountain-head of sci 

 ence ; but the land of Sesostres and Alexander 

 has now become the prey of the ferocious Mos 

 lem ; and whatever she enjoys of art, know 

 ledge or civilization, she is compelled to receive 

 from the once barbarous regions of the West.* 



II. Scientific knowledge will not onlv render 

 persons more skilful in their respective e7r.p.u;. 

 ments, but will enable them to make improve* 

 ments in the arts, and in the physical sciences with 

 which they are connected. 



It has frequently been affirmed that many 

 useful inventions have been owing to chance, 

 and that persons ignorant of science have stum 

 bled upon them without any previous mvestiga- 



* Scots Mechan. Mag. 1826. 



