l62 



NA TURE 



[June 15, 1905 



In such cases it is of course of the greatest value to be 

 able to examine the constitution of the bodies without 

 affecting them chemically ; and spectrochemistry, as we 

 have seen, gives us the means of doing so. By observing 

 the behaviour of light on its passage through the various 

 substances, we gain an insight into their structure without 

 in any way disturbing it. 



In the last ten years the spectrochemistry of the nitrogen 

 compounds has also made remarkable progress. Nitrogen 

 is of the greatest importance as an essential constituent of 

 the proteids, the alkaloids, and many other animal and 

 vegetable products. But its high valency and the extra- 

 ordinary variety of combinations into which it can enter 

 with other elements surround it with special complications. 

 Regardless of these, however, the spectrochemical ex- 

 amination of nitrogen compounds has already vielded 

 useful results, especially in the study of the alkaloids. 

 It is to be expected that this optical method will also be 

 of use in the chemistry of the albuminoids, the study of 

 which is now being prosecuted with so much vigour. 



One class of substances of increasing importance both to 

 science and to chemical industry is that constituted by the 

 natural and artificial perfumes. .\n overwhelming majority 

 of them consist of derivatives of the terpenes. We have 

 already mentioned that Gladstone, in this subject also 

 a pioneer, was the first to study the optical behaviour of 

 the terpenes. Since then the explanation of the structure 

 of these bodies and of a large number of rich natural per- 

 fumes derivable therefrom has been rendered easier by the 

 use of spectrochemical methods. Similar assistance has 

 been rendered to the synthetic preparation of valuable 

 scents, such as ionone, the artificial scent of violets. In 

 every scientific laboratory and in every rationally conducted 

 chemical factory where work is being done on perfumes, 

 the spectrometer is now an indispensable testing instru- 

 ment, and hence also an implement in industrial pro- 

 duction. 



When scientific research opens up new methods of 

 observing nature, it is generally not long before a use is 

 found for the-se methods in practical life. The need is 

 .soon felt of perfecting, and at the same time simplifving, 

 the scientific apparatus. Efforts in this direction have not 

 been wanting in the case of the spectrometer, and they 

 have been crowned with the most brilliant success. 



Prof. Abbe, the distinguished phvsicist who died not 

 long ago, and after him Dr. Pulfrich, constructed spectro- 

 meters on the principle of total reflection. These instru- 

 ments are distinguished from those formerly in use by 

 their extraordinary simplicity and convenience, and they 

 allow also of much more rapid work. 



Such instruments, known as total reflectometers, have 

 been made for the most exact scientific measurements, and 

 also for medical and technical purposes. Special form's are 

 in use for the examination of fats and oils, milk and 

 butter; to determine the amount of salt contained in salt 

 solutions; the amount of alcohol and extractive matter in 

 beer; for the examination of blood and albuminoids in 

 pathological fluids, &c. Several of these ingeniously con- 

 trived instruments give not only the refractive index and 

 the dispersion of a substance immediately, without any 

 calculation, but also directly the percentage of dissolved 

 matter, e.g. of alcohol and extractives in beer. 



THE MIOCENE FORM.iTION OF MARYLAND. 

 y^P- have received from the Maryland Geological Survey 

 a memoir on the Miocene formation of the State in 

 two volumes, text and plates. This is the second of a 

 series of reports dealing with the systematic geology and 

 palaeontology of Maryland, that on the Eocene having 

 been previously published, while reports on other form- 

 ations are in progress. We may heartily congratulate the 

 State geologist. Dr. Wm. Bullock Clark, on the appear- 

 ance of these volumes, which in type and illustrations leave 

 nothing to be desired, while the subject-matter, the result 

 of labours extending over fifteen years, represents the 

 combined work of field geologists and of experts in various 

 branches of pala;ontology. 



Of special interest is a chapter by Mr. W. H. Dall on 

 the relations of the Miocene of Maryland to that of other 

 NO. 1S59, VOL. 72 ] 



regions and to the recent fauna. He points out that the 

 differentiation of faunas in European and North American 

 areas was well established before the beginning of the 

 Tertiary, so that in the early stages of that epoch the 

 faunas in the west show American characteristics clearl\ 

 as compared with those of Europe. Other differences, 

 suggesting migrations, occur in the relative time of appear- 

 ance of certain groups ; as, for instance, in .America, the- 

 first influx of Numinulites is in the upper beds of, the 

 lower Oligocene, just as these lowly forms of life were 

 about to disappear from the European fauna, where they 

 had long flourished. In the history of the .American 

 Miocene there are many differences and many points of 

 agreement with European equivalents, which are duly 

 pointed out. .'\s in Europe, the -Miocene was a period of 

 elevation, of plication of the earth's crust, of denudation, 

 and of the deposition over extended areas of sediment, 

 chiefly of clays, sands, and marls, more or less consolidated. 

 Diatomaceous deposits also occur. 



In an introduction Dr. Clark discusses the general strati- 

 graphic relations of the Miocene deposits of Maryland, 

 which have long been known for the rich faunas which 

 they contain. The Oligocene is not represented, and the 

 strata lie unconformably on the Eocene. The pal<Eonto- 

 logical relations, the subdivisions and geographical dis- 

 tribution of the strata are dealt with by Mr. G. B. 

 Shattuck, who gives an elaborate table showing the locali- 

 ties and horizons of the species. The bulk of the volume 

 is taken up with the systematic paljeontology, the results 

 of an exhaustive study of the fauna, embracing both a 

 critical review of the species described by previous authors, 

 as well as descriptions of a large number of new forms. 

 As remarked by Dr. Clark, the description of species of 

 fossils is of little scientific importance to the geologist, 

 unless the object is something more than the mere multi- 

 plication of new forms. In the present case the endeavour 

 has been made to clear up doubtful points in synonymy 

 and to give as complete an account as possible of the 

 geological and geographical ranges of the fossils. .Ml 

 groups from the Mammalia to the Radiolaria, Foramin- 

 ifera and plants come under notice. The higher verte- 

 brates are dealt with by Dr. E. C. Case, the fishes by 

 the late Dr. C. R. Eastman, many of the invertebrates by 

 Dr. G. C. Martin, the Echinodermata by Dr. Clark, and 

 the remaining groups by other authorities. 



The paleontology is illustrated by 135 plates, while in 

 the volume of text there are sections, numerous pictorial 

 views, and a coloured geological map. The work is well 

 indexed, and there is a useful geological bibliography. 



MINERAL PRODUCTION OF INDIA. 

 A N interesting new departure has been made by the 

 Geological Survey of India in devoting the last issue 

 of the Records (vol. xxxii., part i.) to a review of the 

 mineral production of India during the years i8g8 to 1903, 

 by .Mr. T. H. Holland, F.R.S., director of the Survey. 

 This review, which covers 118 pages, with 6 plates, corn- 

 pares very favourably with the statistics of many countries 

 where the facilities of obtaining information regarding the 

 mineral production are far greater than in India. The 

 period covered is six years, and it is intended in future to 

 issue quinquennial reviews. The minerals are divided into 

 two groups : — (i) those for which fairly trustworthy returns 

 are available, and (2) those for which definitely recurring- 

 particulars cannot be procured. It is curious to note that 

 in the review of mineral production in India issued by [ 



Sir George Watt in 1894, four minerals, salt, coal, iron 

 ore, and petroleum, were the only representatives of the 

 first group, whereas it is now possible to obtain trust- 

 worthy returns of the production of thirteen minerals, coal, 

 gold, graphite, iron ore, jadeite, magnesite, manganese 

 ore, mica, petroleum, rubies, salt, saltpetre, and tin. 



The production of salt, w-hich was 358,000 tons in 1898 

 and 336,000 tons in 1903, showed considerable fluctu- 

 ations during the period under review ; but in the case of 

 all other minerals there was substantial progress. 

 The Indian coal output rose from 4,000,000 tons in 

 1897 to 7,500,000 tons in 1903. The production of gold 

 steadily increased from 390,50; ounces to 603,218 ounces. 

 The production of saltpetre also increased, the average 



