Mdy 8, 1879] 



NATURE 



29 



answered by the fact that, according to Mr. Hill, the epochs of 

 heaviest winter rain are approximately those of highest mean 

 annual temperature. E. DouGiAs Archibald 



Distribution of the Black Rat 



Mr. Middleton's letter in Nature, vol. xix. p. 460, 

 induced me to inquire whether the black rat still occurs in 

 Dresden, the museum undermy care possessing several specimens, 

 which were procured on the spot several years ago. The streets 

 where this rat then occurred being known to me, viz., Meissener- 

 strasse, Alaun-gasse, Konigsbriicker-strasse, all on the right bank 

 of the Elbe, in Dresden-Neustadt, I inquired in many houses, 

 offering a relatively high rewr.rd for a specimen, but hitherto 

 in vain. The museum possessing further a specimen from a 

 place called the Schenkhiibel, about an hour's walk from the 

 town, in the direction of the last of the above-named streets, 

 I had traps put there, but also in vain ; only the brown rat, Mus 

 decumanus, could be procmred. 



Every two years a general rat poisoning being ordered by the 

 magistrate of the town, I shall wait till the next ene (March, 

 1880), and then try to state whether Mus ratlus still lives in 

 Dresden, as it no doubt lived here several years ago. 



The museum possesses besides specimens fromMuhlhansen, in 

 Thuringia, and a series from Saxe-Altenburg ; in the latter 

 country I do not know the exact locality, the man — a dealer — who 

 sent them, being very mysterious on this point, but I have in- 

 dubitable evidence that it still lives there, and even is not rare 

 on some «pots. Knowing that it occurred some time ago in the 

 brewery of Blankenhain Castle, near Crimmitzschau, in Saxony, 

 I inquired there, but got the answer that for two years it has 

 been replaced by At. decumanus. 



Therefore, I am not sure that M. ratlus still lives in the 

 kingdom of Saxony, but I am sure that it occurs in the Saxon 

 Duchiet I shall publish the results of my further inquiries in 

 case they are successful. 



From the Malay Archipelago I brought Af. decumanus, but 

 not Af. rattus. I got specimens from North and South Celebes, 

 besides other localities, but as the Mures in my collections are 

 not yet definitely determined, I cannot give more particulars 

 now. A. B. Meyer 



Roy«l Zoological Museum, Dresden, May 3 



Mice and Beetles 



Permit me to ask, through the medium of your columns, if 

 it is known whether mice kill the common kitchen black- 

 beetle. I have been unable to find anything bearing upon this 

 subject, but having observed that there is an apparent reduction 

 in the number of beetles, or at least no increase in number 

 while the mice are permitted to live, and also that the mice do 

 not touch any articles of food in the kitchen, where they are 

 somewhat numerous, I have been led to think that they prey on 

 the beetles in some way. W. Wordy Beaumont 



The Cause of Thunder 



I HATE lately seen it stated in a text-book upon electricity and 

 magnetism that the phenomenon of thunder is not fully accounted 

 for by any theory as yet brought forward. Whether this be so 

 or not I am not sufficiently acquainted with the subject to say. 

 I believe the commonly accepted theory is that a vacuum is 

 created in the path of the electric spark and that the subsequent 

 in-rush of the air produces the detonation. If, however, it be 

 allowed that the electric spark is not a material substance, but 

 merely a natural force or mode of motion, the possibility of this 

 theory is at once disposed of. 



It is a well-known fact that the passage of electricity in a high 

 state of tension, through a mixture of oxygen and hydrogen, not 

 only causes an explosion, but also causes the formation of water, 

 and it seems to me that, given the existence of free oxygen and 

 hydrogen in the region of the electric disturbance, the pheno- 

 menon of thunder is sufficiently accounted for. 



Whether the normal amount of hydrogen in the air is sufficient 

 to cause the stupendous noi;e of thunder I am not competent to 

 judge, but if not I would suggest that the presence of an abnor- 

 mal amount might be accounted for by the process of the elec- 

 trolysis, which would probably occur between the two poles of the 

 thunder-cloud before the tension became so great as to cause a 

 rupture of the circuit and consequent discharge of the electric 

 spark. I would also draw your attention to the fact that every 



thunder-clap is immediately followed by an increase in the 

 quantity of water deposited in the shape of rain. Does not this 

 point to the formation of water by the explosion of the gases ? 



As I myself am unable both from want of means and time to 

 investigate the matter, I should be glad to find that someone 

 better qualified had taken the subject in hand. It is a frequent 

 experiment of Dr. Tyndall's to show his audience real clouds ; I 

 feel convinced that by following this line of inquiry he could 

 give us a real thunderstorm. S. A. R. 



The April Meteors 



On the night of the 20th these meteors were watched for 

 between loh. 4Sm. and iih. 30m., after which the stars were 

 obscured by a dense fog. During the Jh. of observation 15 shooting- 

 stars were counted, of which 4 or 5 only belonged to the shower of 

 Lyrids. These were faint and somewhat slow, with slight trains 

 and short paths. The radiant point conld not be exactly fixed. 

 Of the other meteors three were brilliant (2 = ist mag. and 

 I = 2nd mag.), and moved with extreme swiftness from a 

 radiant point at 286° -I- 23°. They left bright greenish streaks, 

 and were readily distinguished from the Lyrids, though the 

 radiants lie near together. This new shower near fi Cygni 

 (Albireo) appears to form an important display at this epoch. I 

 saw several bright, rapid meteors from it on April 20-21 last 

 year, and determined the position of its radiant point from a 

 number of shooting-star paths given in Dr. Weiss's two volumes 

 of Austrian observations at 288° -1- 22* (20 meteors) for the 

 period April 19-23 (see Afcnthly Notices R.A.S., vol. xxxviii. 

 P- 396). It is further confirmed by a stationary meteor recorded 

 by Palisa at Troppau on April 19, 1870, at 289-4 + 26°'4, audit 

 will be advisable to look out specially for this prominent shower 

 of swift, streak-leaving meteors during future returns of the 

 Lyrids. The latter display has quite failed during the last few 

 years. W. F. Denning 



Ashleydown, Bristol, April 22 



Salmo salar and the Schoodic Salmon 



Under date of March 13, in the course of remarks on a late 

 report of the U.S. Commissioner of Fish and Fisheries, you 

 express a wish for an explanation of the fact that a sea-going 

 salmon (Salmo salar) was found among the Schoodic p" land- 

 locked " salmon. I take pleasure in supplying the explanation. 

 The fish referred to were taken in Grand Lake Stream, which 

 connects two of the Schoodic lakes, tributary to the St. Croix 

 River, which discharges into an arm of the sea on the border 

 between the United States and Canada. Before the obstruction 

 of the St. Croix by mill-dams, there was nothing to prevent the 

 ascent of ihe sea-going salmon to this stream, and it is among 

 the traditions of the aborigines that they were formerly often 

 taken here along with the nnall " land-locked " or fresh-water 

 salmon. The sea-i-almon they called I'l-lahm ; the land-locked, 

 Tage-wah-iiahn ; and though for many years the sea-salmon 

 were almost wholly prevented from ascending the river by the 

 mill-dams, they have not been entirely exterminated, and the 

 upper waters have been rendered in a degree accessible to the 

 remnant by means of fish-ways constructed within a few years. 



'1 he specimen taken was, at the close of the season, set free 

 with the other captured fish, and doubtless returned to sea. 



I will add that the latest studies of American ichthyologists on 

 the subject have led to the conclusion that the Schoodic and 

 other "land-locked" salmon are specifically identical with 

 Salmo salar (vide Jordan, "Manual of the Vertebrates of the 

 Northern United States," 1878, p. 357). 



Grand Lake Stream, Chas. G. Atkins, 



Maine, U.S.A., April 9 Asst. to the U.S. Commissioner, 



Fish and Fisheries 



Intellect in Brutes 



A FEW months ago I made the acquaintance of a dog, which, 

 I think, is worthy of a place among the dogs, and cats, and rats, 

 and mules that are helping the pages of Nature to determine 

 the degree and kind of animal intelligence. 



" Priest's" is a hotel on Ihe way from the Calaveras Grove of 

 Big-trees to the Yosemite. In former years, on the arrival of 

 the stage, the landlady would send the dog to the poultry yard 

 to catch chickens for the tourists' dinner. Now the dog " takes 

 time by the forelock." The stage is due at six o'clock. About 



