3o6 



SCIENCE. 



[Vol. XXI. No. 539 



candle in a large dark room, in divers positions to this surface, 

 you may exactly represent all the phenomena of these pits in the 

 moon, according as they are more or less inlighted by the sun." 

 He then goes on to advocate the second theory, and concludes 

 finally that the craters had their origin similar to those formed in 

 the alabaster. 



A "tidal" theory, which supposes a time when a thin crust 

 concealed a liquid beneath, which was moved by the action of 

 tides in such a manner as to produce craters, is also examined and 

 rejected by Mr. Gilbert. So also is a "snow " theory, and then 

 are considered the "meteoric" theories, which suppose the pits 

 to have been caused in some way by the impact of extra-lunar 



bodies. As we have seen, this theory was considered and rejected 

 by Hooke in 1667, but others have not seen the same difBculties 

 that he did. Mr. Gilbert advances the following theory : 



" It is my hypothesis that before our moon came into exist- 

 ence the earth was surrounded by a ring similar to the Saturn- 

 ianring: that the small bodies constituting this ring afterward 

 gradually coalesced, gathering first around a large number of nu- 

 clei, and finally all uniting in a single sphere — the moon. 

 Under this hypothesis the lunar craters are the scars produced 

 by the collision of those minor aggregations, or moonlets, which 

 last surrendered their individuality." 



This hypothesis was tested in numerous ways, and it was found 



CALENDAE OF SOCIETIES. 

 Philosophical Society, Washington. 



May 27. — S. P. Langley, On Recent Ob- 

 servations in the Infra-red Spectrum ; G. K. 

 Gilbert, The Average Temperature of the 

 Earth ; Cleveland Abbe, The Formation of 

 Raiu. 



Chemical Society, Washington. 



Apr. 13. — Subject for discussion : Organi- 

 zation as a Section of the American Chemi- 

 cal Society ; G. L. Spencer, A New Drying 

 Oven. The walls of the oven are made 

 double and the space between them filled 

 with a non-conducting substance. The bot- 

 tom of the oven is also made double, the 

 outer wall being made of Russia iron and 

 the inner of copper. The space between is 

 filled with air This oven has lately been de- 

 vised in Dr. Peale's laboratory by Dr. G. L. 

 Spencer. The drying bulbs are made in the 

 shape of a flask with rounded bottom. The 

 content of the flask varies from 150 to 200 

 cubic centimetres. From six to eight of 

 these drying flasks are connected en batterie 

 with the pump. If a current of hydrogen 

 is to be introduced into the drying flask, it 

 is easily accomplished by passing a very 

 small glass tube through the cork, joined 

 to another tube by a rubber connection im- 

 mediately below the cork. The inner tube 

 should pass nearly to the bottom of the 

 flask, passing through a wash bottle con- 

 taining caustic soda, and then through a 

 sulfuric acid bulb. The speed of the cur- 

 rent, which need not be very great, is con- 

 trolled by a stop or pinch-cock. Any of the 

 sample which may touch the inner tube dur- 

 ing the intumesence, caused by desiccation, 

 remains thereon and is weighed at the end 

 with the tube, which is detached and left in 

 the drying bulb. H. W. Wiley, A New Lamp 

 for Securing a Constant Monochromatic 

 Flame. This lamp was devised to secure 

 a constant uniform coloration for polari- 

 metric observations. It consists essentially 

 of two wheels with platinum gauze peri- 

 metres and spokes, driven by a clock-work 

 and mounted as shown in the figure. The 

 sodium salt, chlorid or bromid, is saturated 

 in solution, is placed on the porcelain 

 crucibles to such a depth that the rims of 

 the platinum wheels dip beneath the surface 

 as they revolve. By means of the crossed 

 bands the wheels are made to revolve in 

 opposite directions, as indicated by the 

 arrows. The solution of the salt, which is 

 taken up by the platinum net-work of the 

 -_rim of the wheel, thus has time to become 



perfectly dry before it enters the flame, and j 

 the sputtering, which a moist salt would 

 produce, is avoided. At every instant, by 

 this arrangement, a minute fresh portion of 

 salt is introduced into the flame, with the 

 result of making a perfectly uniform light, 

 which can be used for hours without any 

 perceptible variation. The polariscope 

 should be so directed toward the flame as to 

 bring into the field of vision its most lumin- 

 ous part. The platinum wheels are ad- 

 justable, and should be so arranged as to 

 produce between them an unbroken yellow 

 flame. H. B. McDonnell, A Filter for Fine 

 Precipitates. To prepare the ordinary 

 Gooch filter for the retention of fine pre- 

 cipitates, the writer adds a little powdered 

 asbestos on top of the ordinary asbestos felt 

 in the bottom of the perforated crucible. 

 The fine asbestos can be purchased from 

 dealers in chemicals, and should be an im- 

 palpable powder. It is prepared for use by 

 treating with acid, to remove all soluble 

 matter, and washed a few times by decan- 

 tation. It is kept in water, in which it is 

 suspended, by agitation, just before use. A 

 filter prepared in this manner will perfectly 

 retain barium sulphate, even when it is 

 precipitated cold and filtered at once. 



May 11. — The society amended the con- 

 stitution and by-laws so as to conform it to 

 the requirements of the constitution of the 

 American Chemical Society, in order to be- 

 come a local section of that society. Oma 

 Carr, The Predominant Organic Acid in 

 Acid Juices. A tenacious, diSicultly solu- 

 ble incrustation forming upon the tubes of 

 the multiple-effect evaporator at the Medi- 

 cine Lodge Sugar Works, Medicine Lodge, 

 Kansas, was examined, first with regard to 

 the practical problems connected with its 

 removal, and, second, with regard to its 

 composition, particularly the organic acid 

 in combination with the magnesium and 

 calcium of the scale. The incrustation con- 

 tained a high percentage of organic matter 

 — 54.4 per cent, of which 43.5 per cent was 

 carbon, or 23.7 per cent on the original 

 material. Sulfuric and acetic acid diges- 

 tions of the scale were made, the magnesium 

 salt of the prevalent organic acid isolated 

 and converted into a repeatedly purified 

 lead salt. Combustion of these salts ren- 

 dered results concordant with the theoretical 

 composition of tri- plumbic citrate. Aqueou s 

 solution of the acid gave reactions confirma- 

 tory of the combustions. Inasmuch as the 

 scale may be taken as an indsx of the pre- 

 dominant acid combined with the mag- 

 nesium of the scale, the assumption is plausi- 



ble that the predominant acid is citric, and 

 not aconitic, as has been commonly sup- 

 posed. H. W. Wiley, On the Estimation of 

 Levulose in Honey The principal methods 

 of estimating levulose in the mixtures here- 

 tofore practised are those which consist in 

 the destruction of some of the ingredients 

 in the mixture and the estimation of the 

 remaining one. or the method of Wiech- 

 mann, which consists in the estimation of 

 the polarizing and reducing power before 

 and after inversion. Neither of these 

 methods can be applied to honey, which 

 contains other optically active bodies besides 

 cane-sugar, levulose, and dextrose. The 

 method presented rests on the principle of 

 the change in the specific rotatory power 

 of honey, due to temperature; the other 

 optically active bodies present remaining 

 practically unchanged, as far as specific 

 rotatory power is concerned, with changes 

 of temperature. Polarizations of many 

 samples of honey were made at intervals of 

 10 from to 88. The temperature at 88 

 was chosen as the maximum temperature, 

 because at that temperature a pure invert 

 sugar, composed of equal parts of levulose 

 and dextrose, becomes optically inactive. 

 In other words, the specific rotatory power 

 of levulose at 88 is the same as that of dex- 

 trose. A chart was shown giving a graphic 

 representation of the changes in rotatory 

 power, due to temperature. The chart 

 shows that from 20 to 88 the changes are 

 practically equal for either increments or 

 decrements of temperature. From 20 to 

 there is a slight curve, showing a small de- 

 ficiency in rotatory power at from that 

 which would be calculated from the rate of 

 change from 88 to 20. A table was shown 

 giving the results of the calculation of the 

 per cents of levulose in various samples of 

 honey by this method, which were very 

 satisfactory. 



Reading Matter Notices. 



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