1830,] t 17 ] 



THE PROGRESS OF PHYSICAL DISCOVERY. 



WE could have wished, if our space had permitted, and if their num- 

 ber had been less overwhelming, to have abstracted the principal dis- 

 coveries in the whole field of natural philosophy; but their mass has 

 been growing so large, that an outline of them generally would give 

 but a faint idea of their magnitude, and we are compelled to confine our 

 observations to one branch of the material sciences, viz. the Physical 

 one. The knowledge of the properties of bodies seems a necessary pre- 

 lude to their classification, as performed by geology, zoology, &c. ; or 

 to their application, as in medicine. The progress of physics is conse- 

 quently a good index to our advances in the study of nature in general. 

 It is, moreover, an important element in history ; yet it belongs not to 

 the annals of particular nations so much as to the records of mankind. 

 That memorable epoch, the French Revolution, when the old fountains 

 of government were broken up, and a new state of society commenced, 

 was also the aera from which the spirit of physical inquiry, which has 

 since led to such brilliant results, takes its date. A peaceful revolution 

 in chemical principles was effected in France, whilst her cities were still 

 flowing with the blood of civil warfare. Those principles have been 

 further developed, and made the stepping stones for the discovery of 

 truths of still greater moment, by the philosophers f the rest of the 

 continent, and by those learned men, the memory f whom sheds a lustre 

 on our own country. It is for future ages to signalize the energies of 

 the human mind during the last half century with the distinction it may 

 merit, compared to the years that are to come; but a very slight 

 sketch will enable us to perceive that, with reference to past times, our 

 aera, in its knowledge of nature, and the consequent power of mind over 

 matter, stands unrivalled, and alone. 



The most important and comprehensive principle known in physics 

 is unquestionably that of molecular attraction, upon which depend, sub- 

 ject to the action of heat and analogous causes, the phenomena of the 

 attraction of cohesion, and of chemical, affinity. By these latter are 

 explained the formation of minerals, and the composition of the air and 

 water ; and if the theory of life were revealed, they would also impart 

 to us the structure of living bodies. We are not indeed able to deduce 

 consequences from this great principle with mathematical precision ; but 

 in contemplating one branch of its phenomena, that of crystallization, 

 we seem to have arrived at a degree of certainty with regard to the 

 forms of homogeneous particles when united, which almost entitles this 

 theory to a place in the exact sciences. The difficulty experienced by 

 chemists, prior to 1772> in reconciling the apparent variety of form an 

 salts and stones, was, in some measure, relieved in that year, by Rome 

 de 1'Isle, who first recognised a general form belonging to each species 

 of crystal, from which all others might be deduced, according as their 

 angles were more or less deeply truncated. Gahn, a pupil of the cele- 

 brated Swedish chemist Bergman, soon after observed the regularity 

 with which secondary crystals break off their laminae, and disclose a 

 central nucleus, which coincides with the primitive form of all calcareous 

 pars ; and the Abbe Haiiy having, without communication, made the 

 same remark as Ghan, published his famous Essay on Crystals in 1784, 

 thereby shewing that secondary crystals only differ from their nucleuses, 

 inasmuch as the laminae which envelope the latter diminish in size, 



M.M. Nne Series. VOL. IX. No. 49- D 



