64 



NATURE 



[_May 1 6, 1878 



however, that, as a rule, the dyes most effective are 

 fluorescent, and capable of combining with silver, which 

 may be a help in estimating the reason of the alteration- 

 After referring to other researches of Chastaing and 

 Berthelot, the author glances at the method of estimating 

 the intensity of the chemical rays by the combination 

 between chlorine and hydrogen. The feasibility of this 

 plan was announced by Draper, in 1843, but it was only 

 carried into practical effect by Bunsen and Roscoe, who 

 published their first results in 1853. In 1857 Draper 

 proposed an actinometer based on the decomposition by 

 light of ferric oxalate into ferrous oxalate and carbonic 

 anhydride. " Unfortunately," says the author, " Draper's 

 process, if it leaves nothing to be desired in regard to 

 precision and sensitiveness, is laborious in execution, 

 and is hardly possible in practice." 



A reference is also made to the use of a mixture of 

 oxalic acid and uranium nitrate by Ni^pce de St. Victor 

 for the same purpose, with a statement that with the 

 actinometer employed the readings were very precarious, 

 though by improved apparatus they might be made more 

 reliable. 



Bunsen and Roscoe's actinometer, which, as before 

 stated, depended on the combination between chlorine 

 and hydrogen, is next fully discussed. The various expe- 

 riments made to obtain a proper unit of intensity, to 

 ascertain the absorption of rays due to the chemical 

 operations performed by the light, and the relative effect 

 of the different portions of the spectrum, are well worthy 

 the attention of all workers in this branch of research. 



^. In the next division of the book we have a rhumi of 

 tEe work done by, and the apparatus necessary for, an 

 actinometer dependent on the darkening of silver chloride, 

 the latest form of which was brought out by Roscoe in 

 1874, and is known as his automatic actinometer. 



The substance of the various papers on the subject by 

 Bunsen and Roscoe which have appeared in the Philo- 

 sophical Transactions at different times have been con- 

 densed in a division entitled the "applications chma- 

 tologiques," and very interesting it is. Thus we have an 

 account of the measurement of the intensity of light pro- 

 ceeding from various parts of the sky with the sun at 

 different altitudes ; of a measurement of the intensity of 

 direct sunlight ; the effect of the height of the barometer 

 and thermometer on the amount of chemical radiations ; 

 and of the variation of their intensity at different times 

 of the year and at different latitudes. 



In another division we have a discussion on the 

 actinometer of Roussin dependent on the chemical reac- 

 tion of nitro-prussiate of sodium and ferric chloride ; of 

 Phipson's proposal to employ molybdic acid dissolved in 

 an excess of sulphuric acid ; of Becquerel's ammonium 

 oxalate with mercuric chloride actinometer, and also of 

 his electro-chemical measurer j and finally we have a 

 description of Marchand's researches, which at present 

 have been but little known in England. We suppose it 

 was impossible to close the subject without an article 

 dedicated to " Light and Vegetation," which perhaps is 

 long enough considering how little is really known of 

 these relations. 



We have been thus specific in giving the contents of 

 Radau's little work, as it is in reality the only readily acces- 

 sible account of the classical researches of Bunsen and 



Roscoe. The years which have been occupied in these 

 investigations by these physicists number more than 

 twenty, and it is doubtful if the results obtained have 

 received all that attention from men of science which 

 they deserve. No one who has not been engaged in 

 similar experiments can be aware of the difficulties to be 

 encountered in carrying them out ; that they are great 

 may be shown by the fact that no independent attempt 

 has been made to check the results or at all events there 

 are no published accounts of them. 



The book is a compilation of the results obtained by 

 various persons, and it would be out of place to criticise 

 it in the same way we should if it contained original 

 investigations made by the author. At the same time we 

 may say that there are some few points in the various 

 researches which are open to modification and even to 

 correction, more particularly in those of Marchand. 



BRAIN 

 Brain; a Journal of Neurology. April 1878. Part I. 

 To be published quarterly. (London : Macmillan and 

 Co.) 

 A NEW scientific quarterly has made its debut, en- 

 ■^*- titled Brain, a Journal of Neurology, edited by 

 Dr. Bucknill, Crichton-Browne, Ferrier, and Hughlings- 

 Jackson, names well known in connection with the 

 physiology and pathology of the nervous system, and 

 supported by an able staff of contributors. 



According to the prospectus which has been issued. 

 Brain will treat of the anatomy, physiology, pathology, 

 and therapeutics of the nervous system, from the brain, 

 downwards. The functions and diseases of the nervous 

 system will be discussed, both in their physiological and 

 psychological aspects, but mental phenomena Avill be 

 treated only in correlation with their anatomical substrata, 

 and mental disease will be investigated as far as possible 

 by the methods applicable to nervous diseases in general. 

 The want of such a journal has, say the editors, been 

 long felt ; and, considering the great advances which 

 have been made of late years in the physiology of the 

 brain and nervous system, and the great ignorance that 

 prevails with respect to diseases of the nervous system, 

 even among the majority of otherwise well-informed 

 medical men, we believe the statement well founded, and 

 anticipate a career of great usefulness to the newly-founded 

 journal. In the first number the editors have fulfilled the 

 greater part of their programme, which is stated to 

 include original articles, critical digests, reviews, and 

 abstracts of researches on the nervous system at home 

 and abroad, correspondence on matters relating to neuro- 

 logy, &c. The strength of Part I. lies in its original 

 articles. The first is by Mr. Jonathan Hutchinson, "On the 

 Symptom-Significance of Different States of the Pupil;" 

 the second by Mr. G. H. Lewes on " Motor-Feelings and 

 the Muscular Sense ; " the third by a French contributor, 

 M. Duret, " On the Role of the Dura Mater and its Nerves 

 in Cerebral Traumatism;" the fourth by Dr. Cowers, "On 

 some Symptoms of Organic Brain Disease;" the fifth 

 "On Brain Forcing," by Dr. Clifford Allbutt ; the sixth 

 by Dr. Bevan Lewis " On the Comparative Structure of 

 the Cortex Cerebri ; " and the seventh by Mr. Crochley 

 Clapham, " On Skull Mapping." There are also chnical 



