8 



NA TURE 



\_Nov. 4, 1S75 



The Internal Heat of the Earth 

 On looking over the account, contained in vol. xii. p. 545, of 

 Prof. Mohr's interesting observations on the internal heat of the 

 earth, I found that, according to the law^ which seems to prevail 

 between the depths of 700 and 3,390 feet, there will cease to be 

 any increase at all in the temperature exactly at the depth of one 

 English mile, or 5,280 feet. 



The reason of the discreparcy between this result and that 

 previously given, is to be found in the last entry in your table, 

 where only the upper part of the .stratum 1 etween the depths of 

 3,300 and 3,500 feet, is taken, instead of the whole 200 feet, as 

 in the other strata. 



The following continuation of the table will make this evi- 

 dent : — 



Depth. ^"'^'•"f P" 



•^ 100 leet. 



3300 to 3500 feet 0-445" R. 



3500 „ 3700 „ 0-395 „ 



3700 „ 3900 ,, 0-345 .. 



3900 „ 4100 „ 0-295 ,.' 



4100 „ 4300 „ 0-245 „ 



4300 „ 4500 „ 0-195 ,. 



4500 „ 4700 „ 0-145 ,» 



4700 „ 4900 „ 0-095 ., . 



4900 „ 5100 „ 0045 „ 



5100 „ 5280 „ o- 



By adding the various increments of temperature below the 

 depth of 3,390 feet to the temperature there observed of 36-756° 



R., we obtain 40-81 R., cr 123-82'' F, as the maximum tem- 

 perature. 



To temperature at 



3390 feet = 36-756° R. 



Add at 3400 „ ... ... ... -044 ,, 



3500 , '445 M 



3700 „ 790 „ 



3900 „ -690 „ 



4100 „ -^90 „ 



4300 „ '490 ,, 



4500 ., '390 „ 



4700 „ -290 „ 



» 4900 „ -190 „ 



5100 „ -090 „ 



Between 5 100 and 5280 ... ... "045 „ 



40 -8 10 

 There is a further remaik called for by the manner of filling 

 up the gap above 700 feet. If we compare the increment given 

 for the stratum between 600 and 700 feet, namely I'lo, with 

 that of the next stratum, namely, i "097, we get a difference of 

 only 0-003 instead of 0-05, as in all other parts of the table. It 

 would be more in accordance with the lower part of the table 

 if we could pioceed thus : — 



T-,' .-. Increase per 



I^^Ptl'- 100 feet 



Whether the facts observed will warrant such an extension of 

 the table is a question into which I forbear to enter. 

 Bradford, Oct. 27 John Willis 



OUR ASTRONOMICAL COLUMN 



40 Eridani. — Prof. Winnecke measured, in addition 

 to the well-known distant companion of this star, which 

 is affected with nearly the same large proper motion, two 

 small stars which he calls D and E. It would be inter- 

 esting to ascertain if these stars are fixed, or if they also 

 follow the principal one in its rapid motion through 

 space, and measures taken during the present season may 

 be expected to decide the point. 



The results obtained in 1864 are : — 



AD 

 AE 



Position 



185-04 Distance 75-85 

 312-48 „ 89-45 



If we adopt Miidler's proper motions for 40 Eridani, from 

 the Dorpat Observations vol. xiv., or- 2"- 188 in R.A. and 



— 3*'''470 in declination, we find for 1875, Nov, 15, if D and 

 E are fixed — 



AD 

 AE 



Position 



155-2 ... Distance 41-1 

 336-9 •■• ,. i07"3 



Sir John Herschel had probably in view the physical 

 connection of D and E with their bright neighbour when 

 he suggested that at least a diagram of the relative situa- 

 tion of the small stars near it should be made. 



The comes B which partakes of the large proper motion 

 of A is itself a close double-star, ri. 80 of Sir W. Herschel 

 and 2 518, and Struve first notified its probable binary 

 nature. Dawes refers to the difficulty attending measures 

 in 1 85 1, but the list of epochs is decisive as to rapid 

 orbital motion. We have for comparison — 



4-8 



3 '93 

 !3± 

 3-85 

 4-46 



Dawes estimated the magnitudes of the components loi 

 and II, but there is a suspicion of variability of the 

 smaller one. 



Proper Motion of o^ Centaurf. — The values given 

 in our catalogues for the proper motion of this star in 

 declination are not so accordant as might be expected if 

 only the more reliable or modern observations are used. 

 Thus the Cape General Catalogue has + o"-83, the Mel- 

 bourne General Catalo ^ue + o"'49. 



Perhaps as reliable a figure as any that can be derived 

 from data so far published will be obtained by comparing 

 the declination of the Melbourne Catalogue with that 

 given by the Astronomer Royal's reduction of the obser- 

 vations of the Rev. Fearon Fallows at the Royal Obser- 

 vatory, Cape of Good Hope, 1829-31. With Prof. Peters' 

 elements for precession, this comparison gives + o"-4399. 

 If we similarly compare with Johnson's observations at 

 St. Helena, we find -f- o"-4867. Probably La Caiile's 

 declination has been used in working up the adopted 

 Cape value, as on comparing it with the Melbourne 

 declination for 1870, we should have for the proper 

 motion, -|-o"-723. 



For proper motion in right ascension, the comparison 

 of Fallows and Melbourne General Catalogue gives 

 — 0-52355., and the substitution of Johnson for Fallows 

 alters this to — 0*54623. 



The " ASTRONOMISCHE Nachrichten." — A General 

 Register of the contents of this publication, so indis- 

 pensable to every practical astronomer, from vols. Ixi. to 

 Ixxx., by Dr. C. F. W. Peters, jis announced (Mauke, 

 Leipsic). 



The last number contains the Washington observations 

 of the satellites of Uranus and Neptune during the first 

 five months of the present year, with numerous measures 

 of the position of the companion of Sirius in the years 

 1873-75 ; also, remarks by Prof. Asaph Hall on the deter- 

 mination of the mass of Mars from perturbations of the 

 minor planets, in which Massalia, Echo, Beatrix, and 

 Peitho are mentioned as the planets best adapted for this 

 purpose. Magnifying powers of 610 and S90 were gene- 

 rallv used for the satellite-observations, but on a lew 

 occasions one of 1,290 was employed ; the companion of 

 Sirius was generally measured with 400, all the observa- 

 tions being taken with illuminated wires in a dark field. — 

 The death of Dr. August Reslhuber, so long director of 

 the Observatory at Kremsmiinster, is announced. 



A NEW PALMISTRY 



DR. ALEXANDER ECKER, the well-known authority 

 on matters prehistorical, as well as Professor of 

 Comparative Anatomy in Freiburg, Baden, contributes to 



