May 1, 1899.] 



KNOWLEDGE 



103 



hydrogen, carbon monoxide, benzene, certain cyanogen 

 compounds and tarry products, are also present, and 

 various methods of washing out the most objectionable of 

 these have been used and proposed, such as bubbling the 

 gas through water, sulphuric acid, calcium chloride solution, 

 and solutions of lead salts. 



It is stated that M. Pictet prepares absolutely dry and 

 pure acetylene possessing a distinct, but not unpleasant, 

 odour, having no action on metals, and capable of being 

 compressed without any danger of explosion. 



Although it is not impossible that acetylene may be 

 ultimately applicable for heating purposes, it is at present 

 only in use as an illuminating agent, either in its natural 

 state or after admixture with other gases. 



Prof. Lewes recommends the use of acetylene mixed 

 to the extent of ten %'olumes of acetylene with ninety 

 volumes of a mixture of thirty volumes of methane (marsh 

 gas) with seventy of hydrogen, carbon monoxide or water 

 gas. On the Prussian State Railways, a mixture of one 

 volume of acetylene with three volumes of oil gas is in use, 

 and has been found to pass the tests imposed by the 

 Prussian Government. Acetylene has also been used on 

 trains in Ontario and elsewhere with success, and the 

 United States Lighthouse Board propose to employ it for 

 lighting buoys at sea. The danger of explosion already 

 referred to has, however, given rise to various regulations, 

 which much restrict the use of the gas. The employment 

 of compressed and liquefied acetylene, for instance, comes 

 under the Explosives Act in England, while on the Con- 

 tinent and elsewhere more or less stringent rules are 

 enforced. The action of the English and Continental 

 insurance companies has also much restricted its domestic 

 use. 



The value of acetylene for Uluminating purposes lies in 

 the intense lighting power it possesses, the burner which 

 replaces the ordinary domestic gas burner only consuming 

 about half a cubic foot per hour. The luminosity of the 

 ordinary coal gas flame has, indeed, been attributed by 

 Prof. Lewes to the partial decomposition of the gas 

 into acetylene in the inner region of the flame, and the 

 subsequent combustion of the acetylene : while, according 

 to M. Pictet, the intense light of the acetylene flame is 

 due to the decomposition of the gas mto its elements. 

 This decomposition, which occurs near the base of the 

 flame, is accompanied by the evolution of so much heat as 

 raises the separated particles of carbon to incandescence. 



Apart from any dangers attending the use of acetylene, 

 it has hitherto been found impossible to produce a burner 

 which is entirely satisfactory. Probably, mainly on 

 account of the dissociation of the gas, the nozzle of the 

 burner soon becomes carbonized, and, especially when 

 exposed to draught, growths of carbon soon appear round 

 the nozzle and render the flame so irregular as to make it 

 practically useless. This dilficulty, which is particularly 

 noticeable where no chimney or draught preventer is used, 

 makes it necessary to frequently clean the burner, an 

 objection which very seriously militates against the 

 domestic use of the gas. The burners in use resemble the 

 ordinary coal-gas burners, but have much smaller outlets, 

 some being only the one-hundredth of an inch in diameter. 



Many burners have been introduced to prevent the 

 carbonization referred to, but none have proved entirely 

 satisfactory. The burner of Naphey, of New York, is, how- 

 ever, said to be the best. It consists of two nozzles 

 arranged at such an angle that the thin round pencils of 

 light which they emit meet at an angle of about ninety 

 degrees, where they impinge, and produce an ordinary 

 batswing flame. The nozzles are so perforated that small 

 currents of air impinge on the base of each dame, and 



thus ensure the maximum of oxidation without impairing 

 the light, so that carbonization is minimized. 



Finally, it should be stated that, although much capital 

 has been invested in the acetylene industry, and there is 

 a reasonable prospect of its somewhat extended use where 

 the conditions are not favourable for the employment of 

 other illuminants, this new handmaiden of science is still 

 only on trial, and has many difficulties to overcome before 

 taking the important place among our lighting agents 

 which has been predicted for her. 



CLOUDS. 



By James Quick. 



TO the occasional observer the different types of cloud 

 formed above us appear almost endless. The 

 difficulty he experiences, however, in not being 

 able to assign definite names to them is not sur- 

 prising when one considers the universal attention 

 clouds have claimed throughout the present century. 



Since Luke Howard put forward his classification in 

 1803, there have been proposed up to the present time 

 something like fourteen systems of nomenclatvire, and 

 fiftv or sixty names to designate different cloud types. 

 These, moreover, emanating from most of the principal 

 observatories and meteorologists throughout the world, 

 have demanded their proper consideration and discussion. 

 Howard's system, as will probably be well known, com- 

 prised three different types of clouds. These were described 

 as follow: — (1) Stratus. — " A widely extended, continuous, 

 horizontal sheet, increasing from below." (2) Cumulus.— 

 " Convex or conical heaps, increasing upwards from a 

 horizontal base." (3) Cirrus. — " Parallel, flexuous, or 

 diverging fibres, extensible in any or all directions." 

 Together with these three fumlamental ones, Howard 

 recognized four intermediate forms, compounds of the 

 above. 



Notwithstanding the numerous systems of nomenclature 

 proposed later, none has to any extent displaced that of 

 Howard, which gradually came into general use, and con- 

 tinued so, down to recent years. 



The classification put forward by the late Clement Ley 

 has many points of interest. It claims attention not only 

 as a new system, but also on account of the physical nature 

 of its definitions presenting a clear idea of the several 

 causes of cloud formation. 



Four primary types are here recognized, corresponding 

 to a certain extent to Howard's three fundamentals. The 

 first two, viz., clouds of radiation and interfret, are 

 similar to the original stratus ; the third type — those of 

 inversion — comprise the cumulus ; and the final division, 

 consisting of inclination clouds, correspond to the cirrus 

 variety. These four primary types are split up, making, 

 in all, twenty-six sub-dirisions. 



The Lrenerally accepted classification of the present day 

 is the International system formed from the nomenclature 

 of Hildebrandsson and Abercromby. It is composed of 

 the following ten types and sub-divisions : — 



Low CtODT33. I Middle Clouds. 



1. Stratus. ! 6. Alto-Stratus. 



2. Nimbus. 7. Alto-Cumulus. 



3. Cumulo-Ximbus. I 



4. Cumulus. ' 



5. Strato-Cumulus. i 



Examples of some of these types of clouds are given in 

 the plate. The first photograph is a typical example of the 

 stratus variety, which is defined in the International sys- 

 tem as a lifted fog in a horizontal stratum. The second 

 picture shows the cumulo-nimbus, or thunder-cloud type. 



High Clouds. 



8. Ciiro-Cumulus. 



9. Cirro-Stratu3. 

 10. Cirrus. 



