Oct. 28, 1875] 



NATURE 



565 



On being circuited through 3,500 ^ohms for 23 min., the'E.M.F. 

 rose to I "383. 



More observations were made than those here recorded, 

 readings being taken in some cases every minute, but the only 

 irregularity observed was that noticed when working through 

 30 ohms. 



In these experiments we may notice that when the battery was 

 short circuited through 10 ohms, the E.M.F. after the first two 

 minutes fell 4 j per cent, in i ^ hours ; through 20 ohms it fell 

 3 per cent. ; and through 30 ohms, 2f per cent., in the same time. 

 But when circuited through 100 ohms and upwards, the E.M. F. in- 

 creased with the time,* the percentage increment increasing with 

 the resistance. Hence it appears not unlikely that there may be 

 some resistance through which the E.M.F. will remain absolutely 

 constant ; should this be found to be the case, and should this 

 resistance always remain the same, the battery will be very 

 valuable when required to work through such a circuit. 



It may be remarked that, in accordance with the usual rule, 

 the E.M.F. of the battery increases with the external resistance. 



The cell was insulated for a considerable time previously to 

 commencing each set of experiments. S. A. Saunder 



Cavendish Laboratory, Cambridge 



OUR BOTANICAL COLUMN 



Exotic Timber-trees in Mauritius. — Amongst useful 

 plants that have been introduced into countries distant from their 

 native habitats, the timber-trees are of some interest, inasmuch 

 as beyond the proof of their establishment in foreign climates 

 and soils, some lime is needed to prove what effects the change 

 may have on the quality of the timber itself, for on this alone 

 depends the value of the experiment in a commercial point of 

 view. It is, however, satisfactory to learn that some well- 

 known timber-trees that have been introduced into Mauritius 

 through the instrumentality of the Royal Gardens, Kew, are in 

 a flourishing state. Thus, the mahogany {Swieienia mahagoni), 

 one of the oldest and most valued of furniture woods, has made 

 a very rapid growth, forming, in three or four years after the 

 sowing of the seeds, trees about twenty feet in height, with 

 stems from three to six inches in diameter. In India, likewise, 

 the mahogany thrives well, and as a proof that the wood is 

 valuable, it may be stated that a tree blown down in the Cal- 

 cutta Botanic Gardens during the great cyclone realised over 

 1,000 rupees. Logwood {ILematoxylon camptachianum) is re- 

 ported also to grow well in Mauritius, and it moreover makes 

 excellent hedges, far superior, it is said, to hawthorn. It has 

 been quite naturalised on the hills and waste lands in the vicinity 

 of Port Louis, and annually produces large quantities of seeds. 



Bamboo as a. Paper Material.— A good deal of attention 

 has of late years been directed to new materials for paper 

 making. Esparto has been one of the most successful of modern 

 discoveries, and now we are told that the supplies of that useful 

 Eubstance are decreasing and must in course of time fail alto- 

 gether. Where then shall we look for our future supplies is a 

 question that has agitated many minds, and which has been 

 answered frequently by re'erences to the numerous fibre-producing 

 plants of both ihe East and West Indies, Australia, <S;c. We know 

 that in India the fibrous barks of many trees, and notably that of 

 Daphne papyTactH, are used (or paper making ; while in China and 

 Japan, where paper is used (or a much greater variety of purposes 

 than it is in England, the barks of Broussoneiia papyri/era z.nd B. 

 Kavipferi axe. made into paper of every conceivable and indeed 

 inconceivable form ; for some specimens are so much like leather 

 that it takes a critical eye to detect it, and others are such good 

 imitations of crape and muslin that the same care is needed to de- 

 termine their true nature. That the Chinese and Japanese excel 

 in paper-making cannot be doubted, when we consider all their 

 manufactures, and more especially that fine quality of paper known 

 as India proof paper, which they make from young bamboos. 

 The bamboo as a paper material in this country is a comparatively 

 modern introduction ; indeed, we can hardly say that it has 

 actually become a commercial article, but there seems no reason 

 why the stems of the bamboo, which in tropical countries is one 

 of the commonest and fastest growing plants, should not be con- 



* As the coils were arranged in boxes, and so could not be kept at a 

 uniform temperature, it was thought that this might be due to unequal heating. 

 It was touud, however, that the alteration in the ratio of the resistances due 

 to tliis cause was such as to cause the K.M.F. to appear to increase less 

 than it really did by about '005 per cent, in one hour, which would not 

 affect the results in the tables. 



verted into half stuff ^x\A sent to England in almost any quantity. 

 To make this material better known has been the aim of Mr. 

 Thos. Routledge, in a little pamphlet of forty pages, which he 

 has just issued. Mr. Routledge is no doubt able to speak with 

 authority on the details of manipulation of paper stock in a 

 practical, if not in a scientific sense ; but it is not our in- 

 tention to follow him through the subject, but simply to 

 refer to some facts quoted by him as an illustration of the 

 suitability of bamboo as a paper- making material, and to en- 

 dorse to a certain extent some of those facts and suggestions. 

 Thus, with regard to supply, it is well known that in most 

 tropical countries bamboos of various species flourish to a con- 

 siderable extent and are to the people of immense value, furnish- 

 ing them with numerous articles of daily necessity ; then again 

 their growth is so rapid as to form a constant supply. With 

 regard to the rate of growth, we read that at Gehzireh, the 

 gardens of the Khedive of Egypt at Cairo, it has been known to 

 grow nine inches in one night. At Sion House, the Duke of 

 Northumberland's, stems of Bambusa gigantea have attained the 

 height of 60 feet in twelve weeks ; while at Kew, Bambusa vul- 

 garis is recorded as growing in favourable seasons at the rate of 

 eighteen inches per day ; and at Chatsworth the same species 

 has attained the height of 40 feet in forty days. For the purpose 

 of paper-making the stems should be cut down in a comparatively 

 young state, before they become too woody, and reduced to pulp 

 or hjdf stuff before being sent to this country. 



SCIENTIFIC SERIALS 



American yournal of Science and Arts, October. — This num- 

 ber contains the following two papers read at the Detroit meet- 

 ing of the American Association for the Advancement of Science. 

 — Address of Dr. John Le Conte, the retiring president. — A 

 comparison between the Ohio and West Virginia sides of the 

 Alleghany coal-field, by E. B. Andrews. — There is also a reprint 

 from the Philosophical Magazine of Mr. Mallet's paper on the 

 temperature attainable by rock-crushing. — In an obituary notice 

 of Sir Charles Lyell, there is introduced an extract of a letter 

 from Dr. Mantell to Prof. Silliman, in 1841, describing how- 

 Mantell and Lyell first met. — The original articles in this num- 

 ber are : On the arithmetical relations between the atomic 

 weights, by M. D. C. Hodges. — A note by L. F. Pourtales record- 

 ing the corals found at the Galapagos Islands. — On instinct (?) 

 in hermit crabs, by Alexander Agassiz. This records how 

 young crabs reared without shells during their growth, " made 

 a rush " for them as soon as they were placed in the tank where 

 they were living. — On Southern New England during the melt- 

 ing of the great glacier, Part ii. We reserve our notice of this 

 till the paper is completed. 



Geological Magazine, October. — The original articles are : 

 The Geology of Central Sumatra, by R. D, M. Verbeek (super- 

 intendent of the Geological Survey of Sumatra). TJiis is stated 

 to be the commencement of a series of articles on the sub- 

 ject, published with the authority and assistance of the Dutch- 

 Indian Government The oldest rocks in this part of Sumatra 

 are granites, granite-syenites, and syenites. Then follow sedi- 

 mentary rocks classed as of Carboniferous or Permian age. 

 "This oldest sedimentary formation of Sumatra can be divided 

 into two parts. The lower portion consists of clay-slates with 

 auriferous quartz-veins, marl-slates and siliceous schists ; the 

 upper part consists only of limestone, with some small beds of 

 schists, ' There are quartz porphyries and greenstones, the age 

 of which is not known, but they are probably older than the 

 tertiaries. The tertiaries themselves are divisible into five groups. 

 The trachytic rocks are younger than the tertiaries. Three 

 clearly drawn sections illustrate the paper, and a list of principal 

 papers on the geology of Sumatra is given. — On the origin of 

 Coums, by J. G. Goodchild. That many of these cauldron-like 

 hollows are due to the eddying of ice is the argument of Mr. 

 Goodchild. — Dr. Walter Fhght contimies his "History of Meteo- 

 rites." — Dr. Thomas Wright records the occurrence of the genus 

 Cotylederma in the middle lias of Dorsetshire, 



Poggendorff's Annalen, No. 8. — This number commences 

 with an investigation by Karl Miiller as to the pitch of the 

 transversal vibrations of bars of gypsum, when these are saturated 

 with different droppable liquids. It appears that the Uquid does 

 not act as a weighting of the bar, but enters into imion with the 

 molecules of the substance, diminishing the co-efficient of elas- 

 ticity J and this is manifested in a fall of pitch, the fell having 



