1893.] MICROSCOPIC A 1. Jol'UNAL. 173 



libcrallv. The priiuarv object of its publicntion iiiulouljtedl) is 

 advertising, and were the department as strict with it as with 

 Printer's Ink^ its admission at second-chiss rates would probal)ly 

 cease. But not wishing to seem ungenerous towards what some- 

 body might possibly dream was a rival of ours, we have never 

 before alluded to the subject. W'e do it now only in order to 

 explain a little pleasantr\ which we quote from its columns. 

 Our friends will doubtless share our mirth in reading it. 



"■ H. M. \V has handed us a carefully prepared index to vol. 



ix of the (1S92). Owing to an unexpected delay in getting 



out the December number we were not able to publish it at that 

 time, and to do so now would greatly increase the expense, not 

 only of printing but of sending out this issue, as it could only go 

 at third-cl.iss rates. As the whole ' volume ' is so 'micro- 

 scopic ' in size, and hence articles are easily found therein, we 

 hope our readers will excuse us in the matter." 



Now as they were " not able" to publish the index which H. 

 M. W had so unwittingly prepared, we will ofter to edit and 

 publish it for him for tiie sum of $10, and will guarantee that if 

 the periodical in question is rightfully entitled to go through the 

 mails at all at second-class rate, the index will go too, in any 

 issue in which one cares to send it. 



We have seen copies of the said periodical which had passed 

 through the mails at second-class rates inside of which were 

 folded loose circulars having no connection with the issue con- 

 taining them — the clearest possible violation of the law — and yet 

 we are told that a belated index would subject the issue to third- 

 class rates I Let us lau^fh. 



LETTERS TO THE EDITOR. 



Note. — This column is open to all corresfondents -who write upon tlit 

 topics enumerated under '• Proldrms" or vj ho give other information oj 

 interest. The fact that a problem has been anszvertd once need not deter our 

 friends from makinsr additional comments. To facilitate reference, corre- 

 spondents should cite the number as -well as the page on zvhich have ap- 

 peared letters and queries to T^hich reference is made. The editor is not 

 responsible /or the vievjs oJ others published in this periodical. 



(29) Terrace Dust. — Referring to "Problem" No. 7. page 

 86 of your March issue, I would suggest that the magnetic splier- 

 ules thought to be of cosmic origin might be only cinder-dust, 

 blown to housetops by the wind or escaping from cliimneys with 

 the smoke. SmcIi piirticles would necessarily be fused and be of 

 about the composition indicated in the article on ''Terrace Dust." 

 I have obtained such m:ignetic particles as illustrated in the a^^or'^ 

 article from the sediment found in cisterns in tne following way : 

 A horseshoe magnet was covered with muslin, then fastened to a 

 pole and dragged over the bottom of the cistern. Magnetic par- 



