62 



NATURE 



[Nov. 25, 1875 



bers of the University will of course not be satisfied 

 unless the time of the gardeners is pretty fully occu- 

 pied with decorative floriculture. Comparing such a 

 prospect with the old Garden, one turns to a place whose 

 trim extent is ample for purposes of study, whose old- 

 fashioned aspect is pleasing to the eye without much 

 need of "bedding out," and which is supplied with sub- 

 stantial buildings well adapted for library, herbarium, 

 laboratory, and museum, or which might be made so at 

 comparatively little expense. It is true that the green- 

 houses are dilapidated and antiquated, but they could be 

 reconstructed against one of the old walls, and this at a 

 much less cost than they could be erected in the " Parks." 



The hammer and the chisel resound throughout Oxford. 

 The great court of Christ Church is to be surrounded 

 with useless cloisters. The University Church, having 

 been restored thirty years ago, is to be re-restored in a 

 more critical manner. The beautiful old library of the 

 Bodleian is in no small peril. The secret of all this is 

 easy to read. A new distribution of the funds of the 

 University and colleges is believed to be imminent. From 

 one point of view it is desirable that these should be 

 husbanded to the last penny, in order that new endow- 

 ments for study and research may be adequate and com- 

 prehensive. From the other point of view it is only desired 

 at Oxford siare supra antiqttas vias, and the money must 

 be got rid of before the time of redistribution arrives. 

 Oxford, alas !— and those who regard her most lament it 

 most^has grown careless that her life should pulsate with 

 the life outside her. What new word in science ever now 

 resounds from Oxford laboratories ? Her energies seem 

 lulled in the lethargy of a fastidious, almost feminine, 

 culture. Her professors cannot be denied the possession 

 of capacity and laboriousness, yet if perchance any new 

 teacher is summoned from without to join their number, 

 his friends lament him as one who has fallen away into 

 an intellectual Capua. 



To examine is the crown as to be examined is the com- 

 mencement of an Oxford career. And those who are 

 content that this should be the University's "measure of 

 sufficiency " are only careful that buildings and appliances 

 ancillary to examinations and studies preparatory for 

 them should be after the newest fashion in taste and fitted 

 to excite the admiration of relatives who visit Oxford at 

 Commemoration-time. No one doubts that examinations 

 are useful, and in Oxford, at least, no one will deny that 

 Mr. Ruskin has not written on architecture in vain. But 

 Oxford will not satisfy the hopes of those who look to its 

 treasuries for things new as well as things old, till she has 

 learnt to look upon examinations as by no means a suffi- 

 cient raisoii d'eti-e, and the wisdcm of spending as little 

 as possible upon the decoration, and as much as possible 

 upon the efficient equipment of her workrooms and labo- 

 ratories. 



LOMMEL ON LIGHT 

 The Nature of Light, with a General Account of Physical 

 Optics. By Dr. Eugene Lommel, Professor of Physics 

 in the University of Erlangen. (London : H. S. King 

 and Co., 1^75.) 



''T^H I S book forms the nineteenth volume of the Interna- 



■A- tional Scientific Series. Nearly all the volumes have 



passed through more than one editi<m, and with few 



exceptions the works are of singular merit. They are, 

 moreover, issued at so low a price that they cannot fail to 

 have largely extended an interest in science and given the 

 public a sound acquaintance with the special subjects 

 upon which they treat. In the long list of the forth- 

 coming volumes of the series, we are glad to find that 

 some of the most eminent English and European men of 

 science have consented to take a part. 



In the present treatise, Prof. Lommel has given an^ 

 admirable outline of the nature of Light and the laws of 

 Optics. Unlike most other writers on this subject, the . 

 author has, we thii.k wisely, postponed all reference to| 

 theories of the nature of the light until the laws of reflec- 

 tion, refraction, and absorption have been clearly set 

 before the reader. Then in the fifteenth chapter Proft 

 Lommel discusses Fresnels famous interference experi- 

 ment, and leads the reader to see that the undulatory 

 theory is the only conclusion that can be satisfactorily 

 arrived at. A clear exposition is now given of Huyghens' 

 theory, after which follow several chapters on the diffrac- 

 tion and polarisation of light- bearing waves. The reader 

 is thus led onwards much in the same way as the science 

 itself has unfolded, and this we think is the surest and 

 best way of teaching natural knowledge. 



Let us now look a little more closely at the book before 

 us. It is evidently a translation, and as such the author's 

 meaning must to some extent suffer, but on the whole 

 the translator has done his work fairly well. We regret, 

 however, to meet with some inaccuracies in the use of 

 terms that ought not to have escaped revision. For 

 example, on p. 228 we read : " The intensity (or energ)} 

 of light depends on the liveliness of the vibrations." The 

 word livehness, though used less objectionably in other 

 parts of the book to express brilliancy, is here most hkely 

 to mislead the reader. For liveliness one may take to 

 mean either extent and vigour or quickness of vibration ; 

 if the reader has the former meaning uppermost, he has 

 of course gained a right conception, but if the latter, an 

 erroneous idea is conveyed. The ambiguity of the word 

 is fatal to its use in the passage we have quoted. Again, 

 on p. 250 the -woxAfluids is used when liquids should have 

 been employed ; the passage as it stands runs : " Glowing 

 fluids, between the molecules of which the force of cohe- 

 sion still acts, exhibit a continuous spectrum." This, of 

 course, is not true of elastic fluids^ as gases and vapours. 

 The same error we notice also elsewhere, e.g. on p. 242. 

 Again, on p. 261, the translator makes Prof. Lommel say : 

 " When a telescope is used for the purpose of observing 

 a diffraction image, it is formed in the focal plane of the 

 objective." What is formed ? Surely not the telescope 

 Throughout the chapters on diffraction the term " ele- 

 mentary rays and elementary waves " is incessantl) 

 used ; the more familiar term, " secondary waves," is no' 

 employed ; we think it would have been well to have 

 helped the general reader by a reference to the latter 

 expression in a footnote or otherwise. 



So likewise we find the term "fasciculus of rays" every- 

 where employed, where it is common for us to use the 

 term pencil or group ; it {would have been pleasanter 

 to have varied the expression occasionally by the use of 

 one or other of its synonyms. On p. 249, " consistence 

 of the chord '' hardly expresses with sufficient exactness 

 the word "density" for which it is used, Freshness 



