416 SCIENTIFIC RECORD FOR 1862. 



VI. — a Evaporation : h Condensation; c Rainfall. 



Professor Stokes has so modified tbe Caiui)bell sunsbiue-recorder as to 

 render its use convenient for any ordinary meteorological observer, and 

 thirty stations in Great Britain have been equipped with it by the 

 council of the London Meteorological OfiQce. {Nature, xxiii, p. 113.) 



G. ]\I. Whipple has modified Campbell's sunshine-recorder hy devis- 

 ing a new form of card-supporter. It consists of a light frame, capable 

 of holding a slip of cardboard, to be burned by the sun, in any position. 

 It is arranged so as to receive ordinary parallel strips of card at all 

 times of the year, and to allow of the instrument being employed on 

 any part of the earth's surface without detriment to its efficiency. The 

 card-holders themselves are movable, so as to permit of the cards being 

 changed indoors, or dried, if wet, before removal, in order to avoid mu- 

 tilating the record of observation. The instrument also has an apjdi- 

 ance for placing the card correctly in position to receive the sun's image. 

 {Nature, September, 1881, xxiv, p. 407.) 



An evaporimeter with constant level has been recently described by 

 Professor Fornioni. It consists of an oblong wooden case, with a brass 

 spiral descending into it from a micrometric screw. The spiral carries 

 at its lower end a small glass vessel, which acts as a feeder. A glass 

 siphon extends outwards, horizontal from the feeder, and has at its 

 outer end a small cup, in which evaporation takes place. As the water 

 evaporates in the cup the feeder is lightened, and rises by action of the 

 spiral, thus keeping the level constant. The graduation of the instru- 

 ment is expressed in millimeters of the height of water in the evaporat- 

 ing vessel. {Nature, August 18, 1881, xxiv, p. 286.) 



Mr. John Aitken has read a paper on Dust, Fog, and Mist, that opens 

 up new lines of inquiry, and, indeed, a new future to what has hitherto 

 been one of the most difficult branches of meteorology. Mr. Aitken 

 maintains that dust particles are essential to the formation of rain. He 

 has continued the prosecution of the inquiry, and finds that at the 

 low temperature of 14 °F., equally as at higher temperatures, there 

 is no cloudj" condensation when there is no dust. Cloudy condensation 

 takes place on the dust nuclei, the amount of cloudiness being of course 

 relatively small at such low temperatures on account of the small amount 

 of vapor present. Taken along with Professor Leister's experiments, in 

 which it was shown that a single droj) of rain showed organisms in sen- 

 sitive solutions which would otherwise have remained for months unal- 

 tered, it shows that germ-producing matter, or germs themselves, form 

 at least a part of the cloud and fog producing dust. Hence a cotton- 

 wool respirator may form a protection against disease. {Nature, xxiii,. 

 p. 204.) 



In a subsequent communication Aitken finds that Coulier and Mas- 

 cart had in 1875 arrived at similar results. [And it may be added that 

 since 1871 the present writer has taught his own conclusions, based on 

 general meteorological evidence as well as on chemical and physical 



