ya7i. 30. 1879] 



NATURE 



289 



marking distinctly the commencement and simultaneousness of 

 the storm. 



The disturbance in the vertical force commenced about May 

 14, ih. lom. A.M. (7h. 8m. G. T.), and terminated about 

 3h. 30m. A.M. Between this time and 5h. 45m. p.m. the trace 

 was smooth, but between 5h. 45m, and 6h. 45m. a sharp deflec- 

 tion took place in the opposite direction, the maximum force 

 occurring at 6h. Iim. P.M. (May 15, oh. 9m. A.M. G. T.) ; 

 the deflection or increase amounted to ^^7^ of the vertical force. 



The vertical force trace did not exhibit any of the tremulous 

 motion noticed in the two other curves. 



I may state that a description of the Madison Magnetic Ob- 

 servatory, together with the discussion of the first year's observa- 

 tions and results, is nearly ready in MS. for publication. 



Coast Survey Office, Charlks A. Schott, . 



Washington, D.C., Assistant, C. and G. S., in 



January 6 charge of Observatory 



Migration of Birds— A Suggestion 



I BELIEVE that the migration of birds is one of the most 

 interesting problems to the many who dabble in the narrative 

 branch of natural history. It must also be of some interest to 

 those who study biology in its more strictly scientific form. 

 And yet there appears to be but little accurate information on 

 the subject ; nor, as far as I can discover, have any attempts 

 been made to collect careful simultaneous observations over a 

 wide extent of country, which would appeai- to be the readiest, 

 if not the only means of collecting reliable data. 



I am therefore induced to suggest that you should devote a 

 small space in Nature -weekly, at certain seasons of the year, 

 to the record of observations made in all parts of the world, 

 from which correspondents can be induced to send them, of the 

 passage of any migratory birds. 



The record should, I think, be in a tabular form, giving the 

 place, the date of appearance or disappearance of any migratory 

 bird, the name of the observer, and some few remarks that may 

 appear pertinent, such as the state of the weather, the direction 

 of the wind, the character of the night, whether dark or moon- 

 light, in the case of birds which are supposed to travel at that 

 time. The necessity for recording other facts will no doubt be 

 suggested by those more conversant with the subject. From 

 these suggestions and the experience gained in a short time, 

 detailed instructions might with advantage be framed for 

 observers. The observers should be careful to state whether 

 they were in a position to know with certainty that the date 

 given was that on which the birds really arrived or left, or 

 whether it was the first time their attention had been called to 

 the circumstance. 



I should im^ne yon would soon have a large number of 

 careful observers interested in the subject not only in the country 

 but abroad also. Among these some means should be taken to 

 enlist captains of ships, or other seafaring men. There appear 

 to be few, if any, recorded observations of birds of passage 

 being seen on the wing at sea — though I may be wrong in this, 

 for I do not profess to have gone carefully into the subject. 

 Still, it is curious that one does not hear oftener of flights of 

 such birds as the woodcock, millions of which come to and 

 leave this country every year, being seen at sea, over long 

 stretches of which they are believed to fly. 



J. F. D. Donnelly 



The Formation of Mountains 



The letter of the Rev. O. Fisher in Nature, vol. xix. p. 266, is 

 concltisive as to the more rapid cooling of the interior than the 

 outer crust of a heated globe under the conditions of our earth, 

 and I thank him for clearing up the point. But the question 

 remains, whether the amount of contraction of the interior, and 

 consequent crumpling of the crust, thereby produced in a definite 

 time, is sufficient to account for the elevation of our mountains. 

 It is necessary to take account of the following facts : — 



1. That the greater part of the elevation of all our chief 

 mountain ranges occurred diu"ing the eocene and miocene 

 periods. 



2. The warmer climates of those periods (certainly due to 

 external and not to internal heat) would have tended to diminish 

 the rate of cooling and consequent contraction of the earth. 



3. The Rev. O. Fisher appears to have demonstrated that, even 

 allowing for the total shrinkage due to the earth's cooling for the 

 last hundred milhon years (from a mean temperature of 7,000° F., 



as calculated by Sir William Thomson), the amount of elevation 

 thereby caused would be very much less than that of existing 

 lands and mountains. But we know that these have been 

 lowered by denudation, and again elevated many times over 

 during that period. 



The inadequacy of the alleged cause for the production of our 

 existing mountains would therefore seem to be conclusively 

 established. Alfred R. Wallace 



Mr. Wallace's letters raise three separate dirTicuIties : How 

 can the interior of the earth be cooling faster than its surface ? 

 How can this surface be cooling so slowly (or not cooling at all) 

 as it is assumed to be ? and. How can the different rates of cool- 

 ing of interior and surface account for the corrugations observed 

 in the surface ? 



As to the first question, Mr. Fisher's explanations should 

 remove the difficulty. 



As to the second question. So long as the amotmt of heat 

 radiated firom the siurface into space equals the amount received 

 by the surface from the sun and from the interior together, its 

 temperature cannot fall. The rate of radiation depends on the 

 difference between the temperatures of the surface and space. 

 The supply of heat from the interior depends on the difference 

 between the temperatm-es of the interior and the surface. Since 

 the temperature of the interior is falhng, the supply of heat 

 from interior to sm^ace must diminish. Hence the temperature 

 of the smrface must also fall We cannot doubt that it does, 

 though at present imperceptibly. The extreme slowness is due 

 partly to the fact that the difference of temperature between in- 

 terior and surface must many times exceed that between the 

 siurface and space, even if the latter be at absolute zero ; pardy 

 to the low transmissive powers both of earth and atmosphere ; 

 partly to the immense mass of the earth, from which immense 

 quantities of heat must pass away to lower the temperature of 

 the interior but a trifle. 



As to the third question, whether this small fall in temperature 

 will account for observed corrugations, I will offer no opinion. 

 The size of the earth must be allowed for. A diminution of a 

 foot in radius would diminish the surface by more than nineteen 

 square miles. 



I do not understand why corrugations should lie confined to 

 the surface. I should expect them to extend as deep as the 

 solid crust. They are possible in any stratum which is contract- 

 ing more slowly than interior strata. E. Hill 



St. John's College, Cambridge 



Bees' Stings 



Can any of your readers inform me why the working honey- 

 bee has such an imperfect weapon of defence as its sting mani- 

 festly is ? For piu-poses of self-defence it is apparently worse 

 than useless, for in nearly every case, almost without exception, 

 the bee lays down its life with the sting. The possession of a 

 sting therefore only leads to its own destruction instead of to its 

 preservation so far as the individual bee is concerned. No doubt 

 the hive generally gains an advantage from all its active members 

 having stings and so indirectly do individual bees from the fact 

 that the welfare of the hive, speaking generally, means the wel- 

 fare of the indi\-iduals that compose it. Directly, however, the 

 possession of a sting can only be a disadvantage to the individual 

 bee, unless there are certain enemies from which bees after in- 

 flicting a wound can withdraw their stings and escape with life. 

 This so far as my observations go appears to be very unlikely, 

 and therefore no bee can have any knowledge from experience 

 of what a weapon of offence he possesses for he has never a^ed 

 it, nor can he have knowledge from experience of the conse- 

 quence of using it. All smaller pests bees attack with their 

 jaws. Is it possible, then, that they are so intelligent as to be 

 well aware of the power for mischief to themselves as well as to 

 others which they carry about with them, and that it is only 

 when they altogether lose control over themselves, either through 

 severe pain or through terror lest their queen should be injured 

 that they sign their own death-wan-ants on our hands and faces ? 

 In the death of a few worker-bees a hive suffers very little loss, 

 perhaps none at all ; yet it may have gained much in the shape 

 of seciunty from molestation. Are bees so intelligent as to know 

 this fact and communicate it from one to another, or can their 

 conduct be explained on the lower ground of instinct ? 



It seems that an interesting point is here raised which perhaps 



