386 



NATURE 



{March i6, 1876 



to co-operate in any proceeding which may be thought most 

 1 ikely to induce the Government of the United States to continue 

 the publication of them. Fredk. T. Mott 



Town Museum, Leicester, March 7 



Origin of the Screw Propeller 



I SHOULD like to remark, in reference to last week's letter on 

 the origin of the screw propeller, that I have long considered 

 the pectoral fins, which are so extremely useful to and prominent 

 upon soles, or the family Pleuronedidic, as being highly sugges- 

 tive of this more modern mode of propulsion. Anyone who 

 likes to watch these extremely interesting fish in their swimming 

 movements and graceful gyrations may witness the action and I 

 think attribute to its movements more than is possible in the case 

 of ash and other seed vessels. 



Valentines William Earley 



The Three Kingdoms of Nature 



In reply to your correspondent's question as to which of the 

 three kingloms " water " belongs, I beg to state that the strict 

 scientific definition of a mineral, adopted in most mineralogies, 

 is as follows : a mineral is any inorganic, homogeneous, natural 

 substance. 



This definition obviously includes water, which is accordingly 

 always described in books on mineralogy ; and the fact of water 

 being a liquid at ordinary temperatures cannot of course exclude 

 it from the list of minerals. Indeed, in some mineralogies, 

 gases — such as carbonic acid, sulphurous acid, and even the air 

 —are described as minerals. Water, like many other minerals, 

 can exist in more than one form ; thus, if the temperature of our 

 globe were much lower than it is, we should only have water in 

 the form of the transparent crystalline solid, known as ice, which 

 — like other minerals, such as sulphur, metallic lead, metallic 

 mercury, &c. — has its own particular point of fusion ; thus : 

 sulphur melts at 226° F., water at 32°, mercury at 39°. All 

 these substances still further resemble one another in their capa- 

 bility of being converted into a gaseous form, at certain fixed 

 temperatures. These facts— with many others — prove water to 

 be as much a mineral as calcite or gypsum. E. G. C. 



Upper Holloway, N., March 13 



The Recent Storm 

 Yesterday's storm appears to have been a true cyclone, and 

 to have passed nearly centrally over here about half- past one 

 o'clock. I first noticed the barometer at 11 a.m. I forward 

 observations : — 



Sunday. Barometer. 



10 A.M. Wind and rain S. ... — 



11 „ Strong ditto 27 



12 ,, Ditto from S.W. ... 269 

 12.30 ?..%!. Increased ditto 2685 



I „ Great gale, S. W. ... 26-8 falling still.i 



1.20 ,, Ditto, S.W I At 



1.35 ,, Calm.. {lunch. 



Strong wind from N. ) /-.o 

 with driving sleet.... j ^' 



2.30 ,, Gale, snow and sleet. . 26'85 



3 ,, Ditto, rather increased 26 "9 



4 ,, Brisk breeze, N. ... 27 



5 „ Slight breeze, N. ... 27-35 

 II ., 27-9 



Being a rise i^ inch in|]seven hours. 

 Staplehurst, Kent, March 13 * T. S. Usborne 



Bed-time 



Can any of your readers inform me on what ground the fol- 

 lowing saying is based, and to what extent it is true : — " One 

 hour's sleep before twelve is worth two after." 



March 10 Vita Brevis 



OUR ASTRONOMICAL COLUMN 



Comet 1840 (II.). — In Astronomische Nachrichien, 

 No. 2,079, Dr. Kowalczyk, of Warsaw, publishes his in- 

 vestigation of a definitive orbit for the comet discovered 

 at Berlin, by Prof, Galle, the present Director of the 

 Observatory at Breslau, on the 25th of January, 1840. 



• N.B. — This is -c^ lower than I ever saw it before. 



This comet, which was last observed at Kremsmunster 

 on the ist of April, had already been made the subject of 

 extensive calculation by Professors Plantamour and 

 Loomis. The former, in 1843, discussing his own series 

 of careful observations taken at Geneva, found {Astron. 

 Nach., No. 476) that a parabolic orbit represented the 

 comet's course within the probable limits of error of 

 observation ; on including the series taken at Berlin he 

 found the most probable orbit to be an ellipse, but of 

 great excentricity to which little weight was considered to 

 attach. Loomis, on his side, taking into account the 

 effect of planetary perturbation during the interval of the 

 comet's visibility, also found an ellipse, but with a more 

 moderate excentricity, the period of revolution being 

 about 2.420 years ; the sum of the squares of the errors 

 in the ellipse is diminished to one-third of the amount 

 with the best determinable parabola. Loomis's investi- 

 gation will be found in the " Transactions of the American 

 Academy," vol. viii. ; his orbits are not included in the 

 extensive collection in Dr. Carl's " Repertorium der 

 Cometen-Astronomie," a work which, notwithstanding its 

 great utility to the student of this branch of the science, is 

 yet not complete or free from numerical errors. 



Kowalczyk starts with the parabolic elements obtained 

 by Plantamour in 1843, comparing them with the whole 

 course of observations. After introducing the corrections 

 for aberration and parallax, and the earth's positions from 

 Leverrier's tables, instead of those from the Tables of 

 Carlini use! by previous computers and by the usual 

 method of equations of condition for ten normal places, 

 he finally arrives at an elliptical orbit, very closely agree- 

 ing with observation, and showing a period of revolution 

 of 3,789 years. 



Berliner Astronomisches Jahrbuch, 1878.— The 

 Berlin Ephemeris for 1878 has been received during the 

 past week. In its speciality — the ephemerides of the 

 minor planets — Prof. Tietjen has evidently made a very 

 vigorous and successful effort to keep pace with the fre- 

 quent additions to the list ; his volume contains approxi- 

 mate places for every twentieth day during the present 

 year of 144 of the 160 small planets hitherto detected, 

 and accurate opp)sition ephemerides of 71, occupying 

 together one-third of the entire work. The collective 

 table of elements to No. 147 inclusive is not the least 

 important part of this volume of the yahrbuch. 



Prof. Tietjen continues to transfer to the Berlin work — 

 of course after reduction to that meridian — the places of 

 the moon from our Nautical Abnanac, which, by order of 

 the Admiralty, is invariably published three complete 

 years in advance of t^at to which it applies, and consider- 

 ably earlier than any other of the national ephemerides. 

 The economy of labour of computation thereby effected, 

 which is probably found by the conductor of the Berliner 

 Jahrbuch of material assistance for the production of his 

 extensive work on the minor planets, might possibly be 

 extended in other directions. An ephemeris of the moon 

 from Hansen's Tables, employed for all the European 

 ephemerides, admits of pretty complete check at a small 

 expense of calculation, and there appears to be no advan- 

 tage derivable from an independent work involving such 

 heavy labour as the computation of the moon's positions 

 through a whole year. Prof. Tietjen contents himself 

 with a few direct calculations from the Tables which he 

 says " invariably exhibit a satisfactory agreement " with 

 the results in the Nautical Almanac. 



PHYSICAL SCIENCE IN SCHOOLS 

 A^HEN I claimed for science a position of educational 

 * ^ equality " both as regards range and time with 

 classics and mathematics," I intended to express the 

 afnount of science teaching in the school curriculum 

 which alone can satisfy the upholders of a scientific edu- 

 cation. I am as fully aware as Mr. Wilson is of the 



