May i8, l5 



;.l 



SCIENTIFIC NEVV^S. 



4.61 



and very small pebbles, whilst lower down pebbles 

 of a larger size occur, the intervals between them 

 being imperfectly occupied with any material. This 

 condition he traces to the action of ants, which likewise 

 carry down vegetable matter into their magazines, and 

 do not consume the whole. He estimates that the 

 amount of matter brought to the surface often exceeds 

 three cubic inches per square foot yearly. Thus 

 in fifty years as much subsoil would be brought up as 

 would cover the entire surface to the depth of an inch. 



In damp woodland soils, and alorg rivers, the work is 

 taken up by a kind of cray-fish {Astacus). The same 

 authority estimates that one cray-fish in America will 

 bring up half a cubic foot of earth to the surface in a 

 single season , As these creatures are found in multi- 

 tudes, the total effect of their activity cannot be overlooked. 



Not a few mammals also share in the work of up- 



Apparatus for Generating Carbonic Acid Gas. 



turning, loosening, and aerating the soil. But their larger 

 size is more than counterbalanced by their inferior 

 numbers. We have repeatedlj' been asked by gardeners 

 in different districts why the soil brought up by moles, 

 though fine and loose in texture, was generally infertile. 



It has often, we are informed, been used for "potting " 

 greenhouse plants, but with small success. This, if 

 universally correct, is the more strange, as such mole- 

 earth is brought up only from'depths of, say, four or five 

 inches. On this subject we should be glad of further 

 observations. 



Soil-forming, we thus see, is a task involving the 

 agency of a vast variety of living beings, and its con- 

 sideration cannot fail to impress us with the importance — 

 in many respects the paramount importance — of small 

 things. The subject is worth the attention at once of the 

 geologist, the naturalist, and the practical farmer and 

 gardener. 



APPARATUS FOR GENERATING 

 CARBONIC ACID GAS. 



'T'HE accompanying figure from La Nature represents 

 an apparatus devised by M. Guerit, for the pro- 

 duction of pure carbonic acid on the large scale. The 

 gas is produced in the interior of the copper vessel A — 

 capable of resisting a pressure of several atmospheres — 

 by the reaction of sulphuric acid upon bicarbonate of soda. 

 The two liquids are contained in separate vessels, 

 and are automatically brought into contact at the 

 moment necessary for keeping up a constant pressure 

 in A. The gas, as it is generated, is washed, bubble by 

 bubble, before being made use of The solution of bi- 

 carbonate of soda is contained in A ; B is the apparatus 

 which distributes the dilute sulphuric acid automatically 

 under the action of pressure. M is a pressure-gauge, O 

 an agitator, L the arrangement for washing the gas, and 

 V a cock for running oft" the spent matter, i.e., a solution 

 of sulphate of soda. 



This apparatus was primarily devised for maintaining 

 an atmosphere of carbonic acid in beer-pumps, and in 

 beei -barrels partially emptied. 



THE NEW THERMOGRAPH OF THE 

 ROYAL OBSERVATORY, GREENWICH. 



A NEW thermograph for photographic registration of 

 ■^^ the temperature of the air, and of the temperature 

 of evaporation, by means of the dry bulb and wet bulb 

 thermometers, has lately been erected at the Royal Ob- 

 servatorj', Greenwich, of which, by the kindness of the 



Thermograph at the Royal Observatory, Greenwich. 



Astronomer-Royal, we are enabled to give the accom- 

 panying illustration. It is an improved apparatus, 

 replacing that set up at the Royal Observatory in the 

 year 1848, which was one of the first employed for 

 systematic record by photography of the elements in 

 question. The new apparatus is on the same general 

 plan, the improvement being in details. A fine vertical 

 slit is placed in front of the column of mercury of each 

 thermometer, and the flam.e of a gas-lamp (one for each 



