SECTION XII. 

 METEOROLOGY. 



[THIS Section may be properly divided into three parts. That by Dr. Scoffern, affords a popular and comprehen- 

 sive description of the science. Sucli portion!) of the original paper as referred to Light. Electricity, and Magn. 

 have been omitted, for those subjects have already been discussed in detail, under their respective sections. 'I'm' 

 remarks on Heat and its laws have been left untouched, because, although they have been anticipate! under tluit 

 section, it was thought desirable to bring them again into prominence, in connection with M 

 phenomena. The second part (Chapter IV.), by Mr. Lowe, is devoted entirely to Practical Meteorology, and all.n.ls 

 valuable aid and directions to those who may be disposed to make accurate observations. The third part 

 (Chapter V.), by the Editor, gives a resum* of the proceedings of Admiral Fitzroy and Mr. Glai.-mer, especially 

 in reference to the balloon ascents of that eminent meteorologist ; with other recent and important particulars.] 



CHAPTER I. 

 INTRODUCTION. 



DEFINITION AND LIMITATIONS. The term Meteorology, 

 derived from /itrtwpoc, elevated, was applied by Aris- 

 totle to signify phenomena occurring in elevated regions. 

 It may be considered synonymous with the study of 

 atmospheric phenomena ; though all which concerns me- 

 teors proper is very nearly allied with astronomy. 



In many respects, Aristotle's opinions on meteorologic 

 subjects display the usual acumen of that deep thinker ; 

 his remarks on the subject of dew are particularly inter- 

 esting. Deprived, however, of the barometer and ther- 

 mometer deprived of optical instruments the nature of 

 electricity yet undeveloped, and the composition and 

 functions of the atmosphere unknown, ancient specula- 

 on meteorologic subjects were necessarily unsatis- 

 factory and vague. 



The meteorological writings of Theophrastus, Aris- 

 totle's pupil, were more diffuse than those of that great 

 philosopher, and were long recognised as constituting a 

 text-book. They constituted the groundwork of the 

 Atooinuia, or prognostics of Aratus, and were embodied 

 in a versified rendering by Cicero in his youthful days. 

 Portions of these attempts at versification are still in 

 existence, and do but little credit to the great Roman 

 orator in a poetical capacity. 



Meteorology, in its most common and restricted sense, 

 may be considered synonymous with knowledge of the 

 weather. It therefore involves a full acquaintance with 

 the nature and composition of the atmosphere ; with the 

 laws of gaseous and vaporous elasticity ; with the con- 

 ditions determining the production of fogs, dew, snow, 

 and hail ; also with the laws of atmospheric, optical, and 

 electrical phenomena. It is the province of meteorology, 

 also, to study the phenomena of aerolites, and the rela- 

 tions which subsist between atmospheric conditions, and 

 the development of organic species. 



The above is a general outline of the scope and limits 

 of meteorology. Its successful study will be seen to in- 

 volve a pro acquaintance with many sciences, more 

 especially those of chemistry and electricity. There does 

 in it, indeed, exist any science having limits so undefined 

 as meteorology. From a consideration of the theory of 

 hooting stars, to a contemplation of the mutual alliance 

 subsisting between certain forms of disease and atmo- 

 spheric conditions, or the relation between certain animal 

 and vegetable tribes and given atmospheric conditions, 

 the divergency is wide. Nevertheless, all these branches 

 > id v are intimately allied with meteorology ; and, per- 

 haps, the most delightful part of botanical science is that 

 which seeks to establish connections between the localisa- 

 rt*in vegetable families, in districts charac- 

 terised by tome peculiarity of meteorolngic condition. 

 HurtictilturisU have beeti too ready to overlook the in- 



fluence of remote atmospheric conditions on certain vege- 

 table families. Too frequently it has been considered 

 that a vegetable surrounded by an atmosphere having a 

 temperature similar to that of its native region, and 

 planted in a soil of similar chemical composition, must 

 necessarily thrive. There are, nevertheless, meteoric 

 conditions beyond these. Why is it that many species of 

 the palm tribe refuse to grow very far away from their 

 native regions, although transplanted to localities seem- 

 ingly identical in all respects ? Why is it that 

 palm refuses to grow in regions very far distant from the 

 sea? These questions involve meteorologic considerations 

 of great interest : and not less interesting to a met 

 logist, is the partiality evinced to a restricted region by 

 the cinchona tribe. An atmosphere very much rar 

 .UK I perpetually moist, is so essential to their existence, 

 that they cannot live without it. 



The natural approach to meteorology is the study of 

 the atmosphere, which admits of being contemplated 

 under many aspects. It may be contemplated either as 

 the atmosphere proper or theoretical, composed of two 

 gases oxygen and nitrogen ; or as the practical atmo- 

 sphere or mixture of the gaseous theoretical atmosphere, 

 with numerous vapours, extraneous gases, and fleeting 

 undetermined miasmata. The atmosphere, too, admits 

 of being regarded statically, i.e., at rest ; and dynami- 

 cally, i.e., in motion; the latter involving a study of the 

 causes of winds. The atmosphere, lastly, may be con- 

 sidered in relation to the imponderable agents, to }. 

 light, electricity, and magnetism. We shall begin by 

 investigating the nature of our atmosphere regarded 

 chemically. 



CHEMICAL CONSTITUTION OF THE ATMOSPHERE. By the 

 ancients, air was considered to be an elementary sub- 

 stance. Chemistry at length demonstrated it to consist 

 of two gases, oxygen and nitrogen combined, or rather 

 mixed in the proportions cf about eighty parts, by mea- 

 sure, of nitrogen, and twenty of oxygen ; or, in other 

 words, one volume of oxygen to four of nitrogen. 



Considerable difference of opinion once existed on the 

 ion, whether the atmosphere be a chemical or a 

 mechanical compound. To adduce evidence bearing on 

 tins discussion, would be foreign to the subject of me- 

 teorology. The generally received opinion is in favour 

 of the mechanical constitution of the atmosphere*. The 

 law of the diffusion of gases perfectly accounts for the 

 intimate mixture with oxygen and nitrogen in the atmo- 

 sphere, without having recourse to the assumption of 

 chemical union. An outline of the law in question it will 

 be proper to give. 



Gaseous Diffusion. If two glass vessels be taken, as 

 nted in the accompanying diagram (Fig. 1), the 



