72 



KNOWLEDGE. 



[March 1, 1897. 



ILrttrrs. 



[The Editors do not hold themselves responsible for the opinions or 

 statements of correspondents.] 



THE LEAF.CUTTEE BEE. 

 To the Editors of Knowledge. 



SiKs, — It is gratifying to me to know that my letter in 

 January Kxowledc^e under the above title has amused 

 Mr. Duncan. I hope the following stubborn facts will add 

 to his amusement. 



According to Mr. Duncan's letter in February Knowledge 

 I am "incorrect," "inaccurate," "most misleading," 

 and " distinctly incorrect." My authority is challenged, 

 as well as the quality of the " pudding ' ! 



Now, I reply to this letter with great pleasure. The 

 awkward fact that I have for the past thirty years been in 

 the habit of keeping a diary of facts observed (generally 

 over three thousand per annum), enables me to do so with 

 ease and comfort. 



1st.— I ought to have written "the leaf-cutter bee 

 f/eucrally selects a rose-bush of the ' tea ' type." If Mr. 

 Duncan has a Gloire de I)iion and Jlari'chal Niel growing 

 near to each other, I think the bee would prefer the latter. 

 At some future time I intend to give a complete list of 

 plants and shrubs from which I have seen the leaf-cutter 

 bees cutting the leaves. 



2nd. — I hare seen this bee start a burrow. 



3rd. — / have seen the first piece of (circular) leaf taken 

 down the burrow. 



4th.— 7 hace seen the first piece fixed at the bottom. 



5th. — I hare seen the formation of many cells. 



Cth. — I have seen the thin edge of the wedge-shaped piece 

 put into the saucer-shaped foundation. 



7th. — What I assert I assert on my own authority, 

 from my own personal observations. 



Perhaps the accompanying photograph, which I made 



*» 



Photograph of Pieces of Hose Leaves forming one Cell of Megachile 

 loitliiyhhieUa. 1. Foundation of cell. 2. Cocoon containing 

 larva. 3. Twelve circular pieces as covers, and the last one 

 forming the foundation of tlic second cell. 



three years ago, of the pieces (twenty-nine in number) form- 

 ing one cell, will afford Mr. Duncan more " amusement." 



The statement that the " pudding " was " a dark compact 

 mass, emitting a futid odour," proves that Mr. Duncan was 

 not present when it was being mixed, so he had no chance 

 of trying the quality of a fresh one. 



I do not rely upon every observation made by " well- 

 known scientific men," many of whom copy the observa- 

 tions of their predecessors without testing their accuracy. 

 Abundant proof of this can be given. 



I should be very sorry to write that anyone was 

 "distinctly incorrect," etc., unless I was able to give 

 chapter and verse for such correction. 



My object has always been to endeavour to show to 

 others some of the marvels of insect life which I have 

 been privileged to observe. Fked. Enock. 



STAE SYSTEMS, 

 To tlie Editors of Knowledge. 

 Sirs, — My object in my letter on star systems was to 



show that a close correspondence in the proper motions of 

 heavenly bodies which are situated at immense distances 

 from each other affords no proof of physical connection, 

 even when the resembling motions are of a very unusual 

 character ; while as regards the stars in the Plough, the 

 correspondence has not been shown to be very close, nor 

 are the proper motions of any unusual character. I do 

 not think the parallax of any of these stars has been 

 ascertained with any approach to certainty. But it is 

 undoubtedly small ; and as Sirius and Frocyon are both 

 comparatively near stars, it is not improbable that the 

 actual distance between them is less than that between 

 the extremes in the supposed system in Ursa Major. 

 Physical connection does not, of course, imply common 

 proper motion. Indeed, if one star is moving round the 

 other in a very elongated ellipse, they may be apparently 

 moving in opposite directions. But the converse question, 

 whether common proper motion implies physical con- 

 nection, is the one with which I was dealing. It does so, 

 I think, only on certain conditions, viz., that the stars are 

 situated within a moderate distance of each other, that 

 the correspondence in their motions is close, and that the 

 motions themselves are of such a character that only a 

 small proportion of them can be ascribed to errors of 

 observation. The stars in the Plough do not seem to me 

 to fulfil any of these conditions. W. H. S. Monck. 



SUNSPOTS, 

 I'o the Editors of Knowledge. 



Sirs, — I wish to know, on good authority, the exact size 

 of the sunspot that I am now watching, and which has 

 been on the sun's face (to my knowledge) since January 

 25 th. Can any reader of Knowledge oblige ? 



15th February, 1897. C. T. Hudson, F.R.S. 



[We have seen the sun to-day ! Mr. Hudson's spot is 

 visible, but considerably diminished from what it was on 

 January 25tb. The group consists mainly of an approxi- 

 mately circular spot nearly three degrees of solar longitude 

 in diameter, or twenty-one thousand four hundred miles. 

 Area, three hundred and sixty millions of square miles. 

 At various distances from the main spot are several smaller 

 spots ; total area, eighty millions of square miles. Extreme 

 length, of i/roup, fifty-six thousand miles, — E. W. M.^under.] 



VARIABLE STAES. 

 To the Editors of Knowledge. 



Sirs, — The computed maximum of o Ceti, Mira, following 

 the old terms, fell on November 3rd, 1890, and it again 

 failed of verification. 



But computing from the first observed maximum of last 

 season, January 19th, that phase at the passing apparition 

 should occur on December 17tb, 1896, allowing the period 

 331-6 days to remain constant. 



Beginning a search on September 1st, the star was not 

 found with the field-glass until September 28th, and on the 

 third night following it was lost. In ten days it was found, 

 and then lost for another decade. The failures to find 

 Mira may not unreasonably be attributed to fluctuations 

 in light, and I would not say to the contrary. But in the 

 light of experience it seems better to say that they were 

 due to differences in the condition of the atmosphere — 

 conditions not readily perceived under ordinary circum- 

 stances — for, as a result of my experience, I have a growing 

 belief that, from exact measurements of the light of stars, 

 an observer in the north-east quadrant can predict the 

 formation of a cyclonic disturbance of the atmosphere in 

 the south-west at a distance of over five hundred miles, 

 and indicate its probable intensity and pathway. 



My observations and estimates of the light of Mira for 

 the passing epoch are as follows : — 



