2S0 



KNO^VLEDGE ♦ 



[Sept. 22, 1882. 



giving it a vcr)- martial and rich appearance, in strong 

 contrast with Uie mcKlest brown plumage of its friend and 

 neighbour, the marsh wren. 



Some time ago the writer published an article and 

 illustration of a lish- hawks nest, the interstices of 

 which were filled in with Uie nests of the cow blackbird 

 ((/uMoiVi/* yiirpurfiu^), making a sort of compound nest, 

 or tenement house, of the structure. Following the above- 

 mentioned article was a second, illustrating and descnbmg 

 the strange two-story nest the summer yellow-bird builds 

 to cover the eggs which that tramp, the cow blackbird, 

 delights to surreptitiously deposit in the nests of smaller 

 birds. 



The same young collector that secured the writer the 

 yellowbird's double nest, discovered and brought to him 

 anotlier two-stor)- nest This time botli nests bore unmis- 

 takable evidence of being inhabited. The lower compart- 

 ment, from its peculiar spherical form and the reeds and 

 cat-tail cotton of which it is composed, would be at once 

 Kjcogniscd as the nest of the marsh WTcn, even if it did 

 not contain the little chocolate-coloured eggs of that bird. 

 The upper nest is cup-shaped, three inches inside depth and 

 diameter. The outside is made of coarse straw and fibres, 

 and the inside lined with fine grass. A single glance 

 suffices to prove it to be the nest of a swamp black- 

 bird. 



Two bluish-green eggs, with strange hieroglyphic markings 

 on the end, occupv the upper lloor, and three little brown 

 ^gs are hidden in the lower nest The blackbirds must 

 have commenced the upper nest about as soon as the wrens 

 finished the lower one. 



In both the upper and lower stories of this seaside tene- 

 ment house the eggs were warm when discovered, which 

 proves that tlie mother birds had been off the nests but a 

 ft-w moments. The writer knows of no other recorded 

 instance of a compound nest occupied by the red-winged 

 blackbird and the little marsh wren. 



The sketch on page 279, made from nature, shows the 

 construction and difference in style of architecture of the 

 nests, as well as the ditlerence in the size and appearance 

 of the birds tlicmselves. It is a fact worth noting that in 

 all three instances of compound nests the blackbird plays 

 the part of a parasite in a greater or less degree. 



Edison's L-vmps.— The Edison Electric Light Company, 

 of 71, Coleman-street, E.G., announce that the price of 

 their lamps is now reduced to 4s. each for quantities of 

 100 and upwards, and 48. 6d. each for smaller quantities. 

 These lamps are now being very extensively used in all 

 parts of the glol>e, and there is little doubt but that the 

 company will, before long, earn a rich harvest, thanks, 

 however, as we pointed out some months since, to the 

 quality of tlie labour employed. Even in America, where 

 electricians are, we believe, somewhat plentiful, Mr. Edison 

 has found " he had a greater demand for light than he 

 could supply, owing Uj the lack of experienced men to put 

 in the wires." He also says, referring to the colossal in- 

 stallation in New York, that the loss of current or leakage 

 in six miles of conductors is equal to only -351 of the 

 current necessary to supply one lamp. Several thousand 

 kmps are in the circuit The supply of current is always 

 at hand, and the price V>eing uniform with that charged for 

 ga.s (which, however, is dear in New York), many con- 

 sumers " have ordered out their gas-meters." The Edison 

 li^'ht, which is fitted in one of the wings of the Central 

 T« legraph Office in London, is said to Ix; giving nnlwunded 

 satisfaction. 



CARBONIC ACID IN THE AIR* 

 By M. DrMAs. 



OF nil the pnscs tbnt the ntmosphero contains, thoro is ono which 

 offers a special interest, ns well on account of the part 

 ascribed to it iu the mntuftl intcrchnnKO going on between tho two 

 organic kingdoms, as on account of tho relation that it has been 

 observed to occupy botwoon earth, air, and water ; this gas is 

 carbonic acid. , . , 



Kver since tho fact has been established that animals consume 

 oxygen and give out carbonic acid as the product of respiration, 

 while plants consume carbonic acid and give out oxygon, tho 

 qnostion has often been osked whether tho quantity of carbonic 

 acid contained in tho air did not represent a sort of sustaimng 

 reservoir, which was being continually drown on by the plants 

 and resupplicd by animals, so that it has doubtless remained un- 

 changed owing to this double action. 



On the other hand, Boussingault has long Biuco shown that 

 volcanic regions give out through crevices and fumarolos ouormous 

 quantities of carbonic acid. The deposition of caiboiiate of hrao 

 that is continually taking place on tho sea-bottom is, on the other 

 hand, fixing carbonic acid in quantities which wo may accurately 

 estimate from the strata of limcstono seen on the surface of tho 

 earth Wo might imagine, that in comparison with the hugo 

 volumes of carbonic acid sent forth in volcanic districts, even in 

 tho oldest one, and tho mass of carbonate of lime deposited on the 

 sea-bottom, tho results attributed to tho life of plants and animate 

 would be of no consequence either for increasing or diminishing 

 the physiological carbonic acid in the air comparable with thoso 

 which are accomplished by tho purely geological exchange. 



Schloesing has recently succeeded, by a happy application of the 

 principle of dissociation, in showing that the amount of carbonic 

 acid ill the air bears a direct relation to the quantity of bicarbonate 

 of limo dissolved in sea water. If tho quantity of carbonic acid 

 diminishes, the bicarbonate of tho water is decomposed, half of its 

 carbonic ocid escapes into tho atmosphere, and the neutral carbonate 

 of limo is precipitated. Tho aqueous vapour condensed from the 

 air dissolves part of tho carbonic acid contained therein, and carnoB 

 it along, when it falls as rain upon tho earth, and takes up there 

 enough lime to form the bicarbonate, which is thus earned back to 



' ThTphvsiological role of carbonic acid, its geognostic influenoe, 

 and its relations to most ordinary meteorological phenomena on the 

 earth's surface-all these contribute to give special weight to studies 

 concerned in tho estimation of the normal quantity of carbomc a«id 



'"Nev^r'tholess, this estimation is attended with great difficulty. 

 Not every one is able to take up such (luostions, nud not all pro- 

 cesses are adapted to it. The lirst thought which would naturally 

 ari.se woald be to enoloao a known volume of air in a given vessel, 

 and then determine its carbonic acid by measuring or weighing it. 

 In this way we should obtain tho exact relation between a volume 

 of air and the volume of carbonic acid in it, for any given moment, 

 and in any given place. If, however, this be done with a ten-litre 

 flask, for example, it would only hold 3 c. c. of carbonic acid, weigh- 

 i„L' milligrammes; and, whether it is weighed or measured, the 

 crrnr may easily ecpial 10 per cent, of tho real value, hence no 

 deductions could be drawn from tho observed facts. 



lor this reason larger volumes of air were taken, and a current 

 of air, whose volume could be accurately mt'asurcd by kno\vn 

 methods was passed through condensers capable of retaining tho 

 cartwnic' acid. But in this case tho air must pass very slowly 

 thn.ugh it, BO that the process may lust several hours; and since 

 tho air is continually in motion, owing to vertical and horizontal 

 currents, the experiment may be begun with the- air of one place, 

 and concluded with air from a far distant spot. For example, if an 

 experiment lasting twenty-four hours was made in Pans when the 

 nir moved but four inttres per second (nine or ten miles per hour), 

 it niiifhl bo begun with air from the Department of the Seine, and 

 end with air from the Department of the Uhonc, or the Belgian 

 frontier, according to th 



So long ■ - 



rection of the wino. 



..»« lytical methods of siifiicient dolioacy to 



w'ith"^rtainty't'he 'hundredth, or at least the tenth of a 

 lligrammo of carbonic acid, it was very difficult to determine the 

 titv in tho air at a given time and place 



It 



frequently 



noHHible to analyno upon tlve plain air that has dcHceiided f'omtho 

 heights above, and to examine by bright daylight the effect of mght 



upon the atmosphere. .... ti. 



Htill other difficulties show themselves m such inveBtigations. It 



Hcems very easy to collect carbonic acid in potuah tabes, and t« 



determine its amount from tho increase in weight of thetubcBj but, 



An address before the Paris Academy. 



