132 



SCIENCE. 



[\roL. VIII., No. 183 



satellites, which has now been going on for eight 

 years at the Harvard college observatory, is not 

 mentioned at all. We should like to say a few 

 words here upon the importance of this particular 

 series of observations, which has as yet not re- 

 ceived due justice in print, but space forbids. By 

 the way, the phenomenon of the eclipses of these 

 satellites and their important relation to the 

 velocity of light and the dimensions of the solar 

 system is not referred to at all. 



We regret that the pages concerning the rela- 

 tive value of large versus small telescopes (443 and 

 445) appear in so good a book, and we do not think 

 they w-ould have been so written had the author 

 been a practiced observer. We have not space here 

 to join in this wide discussion, but we would com- 

 mend the author and our readers to the able sum- 

 mary of the case in the letter of Professor Young 

 {Observatory, February, 1886,) as embodying the 

 true gist of the whole matter. Incidentally, the 

 curious misunderstanding of Professor Hall's let- 

 ter {Observatory, May, 1885,) is worth noticing. 

 How any one who has ever used a telescope can 

 read this letter without seeing quiet sarcasm in 

 every line, we fail to see. But our transatlantic 

 neighbors in a body seem to have taken it as 

 written in sober earnest, and the sermons preached 

 from it have been highly amusing, even going so 

 far as to suggest a possible permanent set or dis- 

 tortion in the lenses of the Washington 26-inch 

 since its first manufacture. We advise Professor 

 HaU to preface any future communications of 

 this sort with ' The following is sarcastic,' or other 

 equivalent explanation. 



In the various discussions of reflectors versus 

 refractors, we have looked in vain for a clear 

 statement of the different effect, upon definition, 

 of flexure of the mirror or objective. If gravity 

 bends a lens so that one side is more convex, 

 the other becomes more concave, and the effect 

 upon definition is a quantity of another order 

 entirely from that due to flexure of either side 

 alone ; while the bending of the surface of a mir- 

 ror appears with its full effect upon the definition ; 

 so that a mirror which forms any part of a 

 telescope and changes its position with reference 

 to gravity must be almost infinitely more rigid 

 than a lens in the same situation in order to per- 

 form equally well. This should be borne in mind 

 in such discussions (p. 450). 



Miss Gierke has not touched upon the subject of 

 Mr. Denning's so-called ' fixed radiants ' of meteor 

 streams and the startling suggestions as to the 

 peopling of interstellar space to which the claim 

 has given rise. In the present uncertainty about 

 the reality of the phenomena, perhaps it is just as 

 well. With to-day's doubtful methods of map- 



ping the tracks of meteors, our opinion is that we 

 must wait till some Argus-eyed camera, whose 

 overlapping lenses and plates (mounted on a hem- 

 ispherical surface driven by equatorial clock- 

 work) are sensitive enough to record the paths of 

 all the fairly bright meteors, shall decide, by the 

 doctrine of probabilities, as to the real existence 

 of nine-tenths of the so-called ' radiants ' of to- 

 day. 



Did space permit, pages might be written in 

 praise of the excellent features of the book. But, 

 where so much is good, we consider our limited 

 space better employed in pointing out a part of 

 the minor faults, in order that subsequent editions 

 may be as perfect as possible. Hence, in so much 

 as we may have seemed hypercritical, by so much 

 we trust that the author will consider it a com- 

 pliment to the general excellence and importance 

 of her work. H. M. Paul. 



Washington, July 24. 



It is not a little curious, says the Lancet, 

 that the diseases arising from the wrong use of 

 tea should be met with in greater frequency in 

 countries foreign to its growth. The diseases due 

 to this cause are well known to doctors, but the 

 public seem to be strangely indifferent to the 

 teachings of their medical advisers in these mat- 

 ters. Recently in France M. Eloy has reminded 

 medical men how vast is the number of diseases 

 owing an allegiance to the dominion of Queen 

 Tea. America and England are the two coun- 

 tries that are afflicted most with the maladies 

 arising from its excessive consumption. Individ- 

 uals may suffer in a variety of ways. It is custom- 

 ary to speak of acute, subacute, and chronic 

 'theism,' — a form that has no connection with 

 theological matters. The predominance of ner- 

 vous symptoms is a characteristic of theism. 

 General excitation of the functions of the nervous 

 system may be observed, or the weakness may be 

 noted more especially in the brain as distinguished 

 from the spinal cord. Perversion of the sense of 

 hearing is not at all an uncommon symptom, 

 patients hearing voices that have no real or ob- 

 jective existence. The irritability that overtakes 

 women so frequently may sometimes be clearly 

 traced to an excessive indulgence in afternoon 

 tea. No doubt the tannin which tea that has been 

 standing contains does a great amount of mischief ; 

 but theism belongs, rather, to that class of diseases 

 in which morphinism, caffeism, and vanillism are 

 found. The habit of tea-drinking is one that 

 grows on its victims like the similar ones of 

 opium or alcohol. Taken in strict moderation, 

 and with due precautions in the mode of prepara- 

 tion, tea is, like alcohol, a valuable stimulant ; in 

 its abuse there is also certain analogy. 



