July p, sS.^^S-] 



SCIENCE. 



II 



daylong-, butllie ^ prolongs his day far Into the night. By day 

 his song is not Very musical, but at night it seenia softened and 

 subdued almost t<o"sw eetness. The country boys call him the 

 " sheep'sheep shear-shv -^^''S'lsa'' " bird, as an imitation of his 

 song. The first two no. '^^ are uttered sharply with a considera- 

 ble pause between them t''™' the last very rapidly — nearly run 

 together. 



Two other birds are not ux "icommon night singers — the grass- 

 hopper and henslow's sparrovi '^ (Ammodmmus s. passerinUs and 

 A. hensloivi), especially the latv '^^- His modest little song is go 

 drowned out during the day by tii ^^ larger birds that he must sing 

 at night it he be heard at all. I .^^'^^ often hearf his note Well 

 into the night. 



There is one winter night singer^ ^^^^ chestnilJ- i^ijlored long-' 

 spin (Calcarius ofiiatut): As one waL'"^6'rs over tllug snowclad 

 hills on some frosty night, he may near tL'^ dear chet-iio of this 

 bird starting from the snow where he lies h.i'lden. 



Lynds^ J^nes. 



Oberlln, Ohio. 



The" Earth as a Conductor. 



In reference to the comrtiunication on the use? of the groun^l-'^iB'' 

 an electric circuit, June 1^, you may allow me to say: The ear'ifi' 

 is not a conductor of electricity in any sense, omly as a coxiven-' 

 tion. All Du Moncers measurements, and they were many, gave 

 the resistance of the earth as abaut 100 ohms. TIbbs resistance is 

 negligible in long circuits, telegraphic or telephaniiis, but not in 

 short circuits. 



On the principle of contact electricity (see Ayrtoro and Perry, 

 Jenkins or Gorden) it was wrong to place a copper p'late at one 

 end and a tin plate at the other, as their contact or connection 

 by wire would produce a current along the wire. Kot was it 

 proper to put cliarcoal or carbon or iron around either plate on 

 the same principle. Both plates, preferably, should be of copper 

 surrounded by sulphate of copper. There is considerable resist- 

 ance offered in the passage of a current from one kind &S mate- 

 rial to another (see Jenkin passim). 



The earth may, for convenience, be called a reservoir of elec- 

 tricity, but its quantity is always constant and no eleotricilly can 

 be taken from it at one point without putting an equal quamtity 

 into it at another point. The action or roll of the earth in the 

 ■ circuit is like this. Consider a lake of large dimensions wijtl; a 



Yift and'toroe pump at A connected with a pipe which crosses tlie 

 lake to B;rthe water lifted at A and forced over to B falls into 

 the lake, but not a drop of it ever gets back to A. 



If you will consider a ground wire in a large telegraph or tele- 

 phone ofEoe with a number of circuits of variable resistances and 

 different polarities attached to it you will see that it is absurd to 

 isay that a positive current from one battery goes down that 

 ground wire and off to a distant point while at the same instant 

 a positive current from a distant battery comes up the same wire. 

 That is the common sense view of it, and it is supported by 

 Kirohoff's law, .2 C = 0, or the sum of all the E M F's or currents 

 ■meeting in a point equals nothing. In fact, the ground wire in 

 a large office may be cut (as I have often seen it done for experi- 

 mental proof) without stopping communication. When three or 

 ■ more wires are'joined to the same ground either one of the wires 

 iacts as a return w.ire for the others when the ground wire is cut. 

 -But when all are open at once, then the ground comes into play 

 '■to form the circuit for the first one that closes. It is also useful 

 as a regulator 'Of. current, but the manner of doing this is not 

 :properly introduceable here. 



If nothing -had been s^iid of the use of tin at one end and cop- 

 per at the other the resistance of 102 ohms as found would indi- 

 cate a good ground. ^Butassome current probably arose from 



their use, d6iiht is cast OtJOn the measui'^ffierife Still, on the 

 whole, the grownd was as good as is usually rflSde. 



One hund/ed ohms' resistance in the earth cii'ciiiili OiJder all cir- 

 cumstances s!n!>Uild be reckoned on and may be regarded as a 

 constant. D. FtANEEY. 



Mempbis, Tenn., a'U'ii'sSO. 



On the E WlflWon of the Hdllt of Incubatioii. 



It may be stated au^sl general rule tbitt hftfmless snakf's pf6^ 

 duce their young by me'rlfti of eggs, while jyoisoflous serpents* 4re 

 viviparous, to which fact; ffeey probably ov»e their generic appel- 

 ation of "vipers." The'o'vifiarous snakes, Hfte most other rep-- 

 tiles, deposit their eggs in a' Sii'tmy spot, and tm^et Crduljle them- 

 selves about the incubation, to leave the egg4^ <i6' fetch out as 

 best they may under the inrfilleti'.<* of the sun's J'leaf. There is 

 however, a very carious thougli' annthentic instanctfdh ri^totd of a 

 caged python, in th,* Jardin des' t^hnies, at Paris, v^i\i6]\kfitched 

 otlf her own eggs. She laid fifteen im all, and then cblled'herself 

 around them, and so iJScubated thelw in much the sau'fe' diaft'ner 

 as a setting hen, her terni)erature bei^g observed to inci't'asB j!**- 

 ceptibly d'lWfng the period'. 



This stim*)ge fact, whetheT an ahomSiy or whether a mWfal! 

 Mbit of the' pytfbons, seems to throw cOiM^erable light oc'thfe" 

 e'v'olution of'Khe'iVabit of iucuSdtiOn, so uhi^Msal among bft-Qs/ 

 fdi'it must btfmmembered thai' tlie Wrd ii~cil'.5sely allied to iih'^-' 

 ^h'ptiie, and iifih fact but a highe'r'fdrhi of the «ype. This relW-' 

 tio&^bip is clk^'i^y shown by the st'l'dy'' of the motp'hology of the-' 

 bir.^i b4Tans,- far every part of a bi^fl s bodj' JA*3ut a modification 

 of thi5^orresp0li'llfeg part of the reptfl'^;' itJ-i^^also shown by the 

 fact ti^cit birds ar'*- iVgund in geological' 'sfraMTfei mediately after 

 the repiiles," and hewo-e must have appeared' Up'.^f'the face of the 

 earth at a later'peitodv Were any furtbyf'pl-obfi necessary, it is 

 furnished-in ati''irrefLit6il)le manner by th^'sciehce- ef embryolo- 

 gy, for the bitd passes liw the egg through aM'the reilttiian stages 

 of development- beforg" ife is finally hatch-JS 'otitini its perfect 

 form. 



This being th^caSe, v^e'may rest assured th*f *tfiV-haBfit of in- 

 cubation has be'in'ev'olt'ed-iaft some time during the evolhtjion of 

 reptiles into birds, ahdihenoa- this case of the pytiion 'Hat'chang its 

 own eggs acquires-e'xeeptions8 interest. 



We may premise that'thehafoit could never have been evoflved 

 unless it were of soCne valbe-to the species, but we miist' at 3he 

 same time admit that' the incubated egg would in all'caaes-hat'irii 

 out far in advance of' that' heated only by the sun, hence those 

 individuals which thus appeared? earlier than their brothers i-an a 

 better chance of surviving in the struggle for existence. So far^ 

 so good, but how did the babic originate ? What first led siiakes- 

 or other reptiles to think of hatcfiing out their eggs'? That it 

 was not intelligence we can safely assert, for all who have hadi 

 any experience in keeping snakes, a^ree in stating that their in- 

 telligence is of the lowest order. I am therefore inclined to be- 

 lieve that what first led animals to incubate their eggs was the- 

 lieat developed in the egg during the process of hatching. Snakes- 

 are exceedingly fond of heat, in fact I have known them to in- 

 jure each other in cages in the attemipt to retain the warmest 

 places. Hence we can infer that if, when basking in the sun, a 

 snake chances to lie near its eggs, especially if these have already 

 begun to hatch, it will soon feel their heat and so be led to coil 

 more closely about them, and while thus warming itself it will 

 at the same time hasten the process of incubation. 



The next question that arises is, how this habit of incubating 

 her eggs, even when thus acquired, will be ti-ansmitted to the off- 

 spring, for if not transmitted, the habit could never become 

 general. 



So little is known of the principles of inheritance that we can- 

 not hope to solve this problem at present. Even Darwin, who 

 made a life-long study of the subject, and to whom we are in- 

 debted for the ingenious theory of pangenesis, was forced to ad- 

 mit our abject ignorance of the laws of transmission of characters 

 from parents to children. We can, however, infer that those 

 serpents most susceptible to the cold would be most likely to re- 

 main by their eggs, and this susceptibility to cold would tend to 

 be inherited by the voun.g 



