May i, 1SS4 



NA 7 URE 



2 3 



he collimator proposed in 1S57 was made for it last autumn by 

 [r. Howard Grubb, M.E., F.R.S., and its performance has 

 icen fully tested with the most satisfactory results during the 

 jresent observing season. The new collimator is a short tele- 

 :ope of eleven inches focus and two inches aperture, which, 

 hen used, is to be inserted into the eyepiece-holder of the large 

 elescope. A spark between platinum points is produced in the 

 bcus of this instrument by a small Rhumkorff's coil such as 

 hose sold with toy apparatus, and the light of the spark emerging 

 "rom the collimator is reflected by the small mirror of the New- 

 tonian, and so reaches its large mirror. By pushing the eye- 

 jpiece and platinum points of the collimator a little inside its 

 Ifocus, the beam of light, as it passes down the large telescope, is 

 [rendered slightly divergent, and falls normally on the large 

 jmirror. If everything is in perfect adjustment, the beam of 

 'light will then, after reflection by the large mirror, retrace its 

 isteps, and, reentering the collimator, will form an image coin- 

 cident with the spark. Any want of adjustment is at once be- 

 J trayed by the image in the field of view of the collimator not 

 being coincident with the spark. On commencing the night's 

 observing, the mirrors of the large telescope are first adjusted in 

 the usual way. The collimator is then put into the eyepiece- 

 holder, and if the telescope has been tolerably well adjusted, the 

 image of the spark will be found not farther from the spark than 

 a quarter or a third of the field of view of the eyepiece of the 

 collimator. The adjustment is then completed in the following 

 way : — The eyepiece-holder, instead of being rigidly attached to 

 the tube of the telescope, is mounted on a triangular plate fas- 

 tened to the side of the telescope by screws acting against springs 

 U the corners. 1 :hese screws the line of collimation of the 

 eyepiece-holder can be slightly altered, and by moving them the 

 image of the spark is made to coincide with the spark. The 

 instrument is then in a condition of optical adjustment vastly 

 more perfect than has hitherto been attainable with reflecting 

 telescopes. This whole process occupies less than half a minute, 

 and is so easy of application that the author is in the habit of 

 repeating it every time the telescope is moved to a fresh object. 

 He is rewarded by having the last degree of refinement applied 

 to the adjustment of his telescope in using it upon every 

 object, an advantage the importance of which will be ap- 

 preciated by every astronomer who uses a sufficiently fine 

 mirror and is working on a sufficiently good night. — Mr. 

 J. Joly, B.E., read a paper entitled "Noti - on a Mi 1 

 scopical -Examination of the Volcanic Ash from Krakatoa." 

 The ash examined was part of some which fell on board the 

 Norwegian barque Borjild while she lay at anchor off the great 

 Kombuis Island on August 27, 18S3. Her position was some 

 75 miles to the north-east of Krakatoa, a strong south-westerly 

 gale prevailing at the time. She was hence most favourably 

 placed for receiving good samples of the dust. A specimen of 

 the floating pumice, picked up by the Borjild in the Straits of 

 Sunda, was compared with the ash. Microscopically they were 

 found to present the same features. Two species of pyroxene 

 occur — a monoclinic and a rhombic variety. The first was 

 augite ; the second presents many of the optical characteristics 

 of hypersthene. Both contain much magnetite. A triclinic 

 felspar is very abundant, showing many different crystalline 

 shapes. The identity of many of these with the triclinic felspar 

 is shown by their occurrence, twinned with and superimposed 

 upon crystals presenting undeniable plagioclastic characteristics. 

 They show small angles of extinction. The presence of sana- 

 dine appeared doubtful. Iron pyrites was found in the ash, 

 both embedded in vitreous fragments and free, as aggregations of 

 cubes, showing the striations at right angles for adjacent faces. 

 Magnetite is abundant. The frequency of lines of growth on 

 the felspars seemed indicative of a comparatively tranquil forma- 

 tion. Most of the crystals showed a fine coating — much pitted 

 and reticulated — of vitreous matter. A sudden mechanical 

 separation from a viscous magma would explain this appearance, 

 which somewhat resembled that produced by rapidly separating 

 two flat surfaces compressing a viscous substance. Organic re- 

 mains were found abundantly in both ash and pumice. A 

 foraminiferal shell, very perfect, was found in the ash, and an 

 other in the pumice. Fragments, apparently of some algae, 

 were found plentifully in the former. — Dr. R. S. Ball, F.R.S., 

 exhibited Mr. Common's photograph of the great nebula in 

 Orion.— Prof. G. F. Fitzgerald, F.R.S., exhibited Ayrton and 

 Perry's new spring ammeter. 



Section of Natural Science, W. Frazer, F.R.C.S.I., in the 

 "hair. — On spherical or globular phosphorites of Russian Podolia, 



by Prof. J. P. O'Reilly, C.E.— Catalogue of Vertebrate fossils 

 from the Siwaliks of India, by R. Lydekker, B.A., F.G.S., 

 F.Z.S. Communicated by V. Ball, M.A., F.R.S.— On the 

 action of waves on sea-beaches and sea-bottoms, by A. R. Hunt, 

 M. \.. F.G.S. Communicated by Prof. A. C. Haddon, M.A., 

 F.Z.S. After detailing the conflicting views put forward by 

 various authors, Mr. Hunt discusses Mr. Scott Russell's theory 

 of oscillatory waves being converted into waves of translation, 

 with observations and experiments to disprove it. The author 

 then treats of the action of waves, currents, and wind currents 

 on beaches, shingles, and sandbanks as observed in the neigh- 

 bourhood of Torquay, and describes experiments conducted in a 

 specially constructed tank. 



Edinburgh 

 Royal Physical Society, April 23. — Dr. Traquair, F.R.S., 

 in the chair. — Mr. Hugh Miller, A.R.S.M., read a paper on 

 boulder-glaciation and striated pavements. Starting from local 

 observations made near Edinburgh by Charles Maclaren and 

 Hugh Miller upon the glaciation in situ of boulders and boulder 

 pavements in the till, the author has been led to the conclusion 

 that boulder-glaciation in situ, registering the ice-movement dur- 

 ing the formation of the till, is extremely common. The glacia- 

 tion of the county of Northumberland, to wdiich he referred in 

 passing, may be roughly divided into upland-glaciation, valley- 

 glaciation, and glaciation of the seaboard. All these are regis- 

 tered equally well in the striation of the larger boulders (whether 

 singly or in groups) as in that of the rock below. He confirmed 

 the older observations that the glaciating agent was the same in 

 both the rocks and the boulders, adducing the fact as strong 

 evidence of the glacier origin of the deposit. That floating ice 

 should striate in fixed directions so many blocks lying in soft 

 mud at the sea-bottom he regards as impossible. As registering 

 changes in ice-movement, the intercrossing of erratics, and a dis- 

 tinction between successive boulder-clays, this widespread glacia- 

 tion of boulders in situ may prove of general importance and a 

 distinguishing mark of the true till. 



Paris 

 Academy of Sciences, April 21. — M.jRolland in the chair. — 

 Letter of condolence to the family of the late M. Dumas from 

 the savants of Geneva. — On a theorem of Kant relating to the 

 celestial mechanism, by M. Faye. — On the scale of temperatures 

 and on molecular weights, by M. Berthelot. The author en- 

 deavours to show that a profound study of specific heats tends to 

 establish the fact that heat, which resolves compound molecules 

 into their elements, has also the effect of resolving the highly 

 complex groups of particles which constitute the bodies hitherto 

 regarded as elementary. — On the optical identity of the crystals 

 of herderite of Ehrenfriedersdorf with that of the State of 

 Maine, by M. Des Cloizeaux. — Account of a young gorilla 

 recently brought from the Gaboon and now in the menagerie of 

 the Natural History Museum, Paris, by M. Alph. Milne- 

 Edwards. This specimen is described as of a much more 

 ferocious character than the chimpanzee or orang-utan, and 

 greatly inferior in intelligence even to the gibbon. — Note accom- 

 panying the presentation of the marine charts and hydrographic 

 documents offered to the Academy by the Depot of Charts and 

 Plans on behalf of the Department of Marine, by M. de 

 Jonquieres. — On the separation of phosphoric acid in arable 

 land,, by M. de Gasparin. — On the speed attained by Lapps 

 with their snowshoes ; extract from a letter addressed by M. 

 Nordenskjbld to M. Daubree. From the result of races insti- 

 tuted for the purpose of determining this point, an average speed 

 of over six miles per hour was verified at Quickjock in Lapland. — 

 Further observations on the present appearance of the planet 

 Uranus as observed at the Observatory of Nice during the month 

 of April, by M. Perrotin. — Changes observed in the rings of 

 Saturn, by M. E. L. Trouvelot. From continued observations 

 made since the year 1875 at the Meudon Observatory the author 

 is able definitely to confirm the conclusion already arrived at, 

 that the rings, so far from being fixed, are extremely variable.— 

 On surfaces of the third order, by M. C. Le Paige. — On uni- 

 formly inclined surfaces and proportional systems, by M. L. 

 Lecornu. — On the principle of the prism of greatest thrust, laid 

 down by Coulomb in the theory of the limited equilibrium of 

 sandy masses, by M. J. Boussinesq.— On the diffusion of light 

 through unpolished glass or metal surfaces, by M. Gouy. — On 

 the propagation of sound through gases, by M. Neyreneuf. — On 

 the boiling-point of oxygen, air, nitrogen, and the oxide of car- 



