36 



I'oftrLAli sci:fcisrcE is^eWS. 



[March, 1S89. 



made the electrolytes solid, and the partition elec- 

 trolytic. The results obtained by the use of this 

 non-porous partition are reported to be highly sat- 

 isfactory, so that very nearly the entire theoretical 

 amount of energy contained in the zinc is obtained 

 as current in the external circuit, due to the absence 

 ol local action, even when the cell remains idle for 

 long periods of time. 



THE COLORATION OF A COAL FIRE BY 

 COMMON SALT. 



It is probable that many persons have, like my- 

 self, been questioned as to the cause of the blue 

 flame produced when a pinch of ordinary table salt 

 is thrown into a coal fire. I have, however, never 

 met with anyone who could explain the phenome- 

 non, which appears to contradict the results of the 

 usual experiments on flame colorations, in which a 

 spirit or gas lamp is used. Among the attempts at 

 explanations which I have heard suggested are : — 

 (i) That the vapours arising from the salt prevent 

 complete combustion, the blue flame of carbon 

 monoxide being the result. (2) That the sodium 

 flame cuts ofl"the yellow light emitted by the glow- 

 ing coals, and only allows the red and blue to pass. 

 (3) That the coloration is due to the chlorine of 

 the salt, which may perhaps combine with the car- 

 bon and hydrogen of the fuel to form compounds, 

 such as chloroform and tetrachloride of carbon, 

 which are, in their turn, decomposed and oxidised, 

 with production of the coloration in question. 



The blue coloration seems to me to be of too 

 purple a shade to admit of the truth of the first 

 theory. The second theory seems rather far-fetched, 

 but the third is pretty well borne out by the follow- 

 ing facts, the result of some experiments which I 

 have recently made : 



1. The blue flame is not produced when sodium 

 chloride is projected on to a red-hot platinum cap- 

 sule. 



2. The coloration produced by throwing sodium 

 chloride into a coal fire is produced equally well by 

 potassium chloride, and less readily by the chlorides 

 of barium, calcium, and ammonium. 



3. The coloration is not produced by the car- 

 bonate, phosphate, or sulphate of sodium. 



4. Chloroform, carbon tetrachloride, and ethy- 

 lene dichloride, when thrown into a coal fire, pro- 

 duces blue colorations, similar to that produced 

 by sodium chloride. — -Norman Leonard in Chemi- 

 cal News. 



SOME OLD TREES. 



The old oak tree at Waltham, which so excellent 

 an authority as Prof. Alexander Agassiz said was 

 700 years of age, has been cut down. It has been 

 dead for some time, and stood in the path of modern 

 improvement. Part of the venerable tree will be 

 preserved in the library. 



The great oak tree at Woodbridge, which was cut 

 down a few weeks ago after an existence reckoned 

 at from 1500 to 2000 years, is to be made into chairs 

 for the members of the Qiiinnipiac Club of New 

 Haven. This tree was doubtless the oldest along 

 the Atlantic coast, although the authorities differ 

 as to its age, and the largest oak in the world. 

 Oliver Wendell Holmes said the tree was at least 

 1800 years old, and Prof. Abbott of New York, who 

 made a careful examination of the monster eighteen 

 years ago, said it could not be less than 2000 years 

 old, while Prof. Eaton stands with these authorities 

 by stating the age of the tree as ranging from 1500 

 to 2000 years. 



'»> 



AN APPARATUS FOR STUDYING INSECTS 

 UNDER GROUND. 

 Prof. H. J. Comstock of Ithaca has, by a very 



simple invention, greatly extended the field of in- 

 vestigation for entomologists. He has made it pos- 

 sible for them to see insects under ground, and 

 study their subterranean habits. The apparatus 

 consists of a narrow frame made of wood, the two 

 broad sides enclosed with glass. A sheet-iron shut- 

 ter or screen is fitted to slide before the glass on 

 each side, and, at ordinary times, exclude the light. 

 Two sides and the bottom of the box thus formed 

 are therefore narrow, and composed of wood, while 

 the other two sides are broad pieces of glass. The 

 top is open. 



• This box is filled with earth, and any plant that 

 may be selected is set out in it. The insect living 

 under ground that is an enemy of this plant, and 

 whose habits it is desired to study, is also placed in 

 the earth. The sides of the box are then closed 

 with the screens, so as to secure the same conditions 

 in the soil in the box as under ground in nature. 

 From time to time, as it is desired to investigate, 

 the screen on one side is temporarily removed, and 

 through the glass the movements of the insects may 

 be observed, changes in their development noted, 

 and important discoveries may be made. 



The apparatus is made of all sizes and various 

 shapes, so as to adapt it to any special investigation 

 that may be undertaken. Professor Comstock has 

 one at Ithaca so large that he keeps it in a hole in 

 the ground, and raises and lowers it by means of a 

 rope attached to a pole. It is admirably adapted to 

 the study of the roots of growing plants, and may 

 be so modified as to expose to view the underground 

 habits of small animals that burrow. — Science. 

 <♦> 



THE TELAUTOGRAPH. 

 Prof Elisha Gray seems to have nearly, if not 

 quite, perfected the telautograph, or writing tele- 

 graph. Professor Gray's device consists of two cur- 

 rent interrupters at the sending end, and a pair of 

 electromotors at the receiving end. The sender uses 

 either pen or pencil, near the point of which are at- 

 tached two threads running at right angles to each 

 other. These threads are kept at an even tension 

 automatically, and each one passes to a current in- 

 terrupter set into the telegraphic circuit. When the 

 pen moves to the right the current is broken a great 

 number of times for a small movement. When it 

 moves to the left the current is reversed, and is sim- 

 ilarly interrupted. The same arrangement prevails 

 on the movement of the pen up and down. The 

 writer can write or sketch as rapidly and as freely as 

 if he had no telegraphic attachment. At the receiv- 

 ing end there are two electro-magnets, fitted with 

 rods set at right angles to each other, so pivoted as 

 to give any motion desired to the pen which they 

 carry at their intersection. When a series of breaks 

 in the current is caused by a motion of the sending 

 pen to the right, the magnet draws the lateral rod 

 also to the right. Similarly, upward motion is given 

 by the vertical rod. Left-handed or downward 

 strokes of the sending pen are reproduced by the 

 receiving pen in the same manner. Consequently 

 every motion made on the paper at one end of the 

 wire is copied at the other end. When the pen is 

 taken oflf, or a new line is begun, an automatic device 

 operates with the same result on the receiving pen. 

 — Engineering and Mining Journal. 



DETECTION OF ANTIMONY IN MINERALS. 



By adding a drop of ammonium sulphide to the 

 white incrustation of SbaO.'s obtained by heating the 

 antimoniferous mineral with fusion mixture in the 

 inner blowpipe flame, I have shown how antimonv 

 can be rapidly and surely detected. When the anti- 

 mony is present in very small quantity, the charcoal 

 method must be the one adopted. In other cases, 

 however, when the metal is more abundant, it can 



be quickly and very satisfactorily identified by heat- 

 ing the substance, with the addition of fusion mix- 

 ture, in a glass tube (having about 1-4" bore) open 

 at both ends. A little of the mixture of pounded 

 mineral and flux is placed in a glass tube at a dis- 

 tance of about a quarter of an inch from the end. 

 The tube is inclined slightly, and heat by means of 

 a blowpipe flame is applied. Dense w-hite smoke is 

 produced, and a white sublimate deposits on the 

 upper and sometimes also on the lower side of the 

 tube. Touch this white sublimate with a single 

 drop of ammonium sulphide, and at once the highly 

 characteristic orange sulphide of antimony is pro- 

 duced very distinctly. No other white sublimate 

 obtained in the open tube in the manner described 

 than SbaOa, is converted into an orange-colored sub- 

 stance on the application of ammonium sulphide. — 

 Chemical News. 



SCIENTIFIC BREVITIES. 

 Action of Electricity on Dust. — M. Soret 

 of Geneva, shows the deposition of dust by elec- 

 tricity in the follow ing manner : He [Waces a plati- 

 num cup full of water in a dark chamber, and con- 

 nects it with one pole of an influence machine, 

 while the other pole is fixed at any convenient dis- 

 tance above the surface of the water. The water is 

 then heated with a Bunsen burner, and its surface 

 strongly illumined by an arc light. As the water 

 boils, the vapour is distinctly visible in the lumi- 

 nous beam ; but on setting the machine to work it 

 is re-precipitated on the edges of the cup. By plac- 

 ing the upper pole sufficiently near the surface of 

 the water the whole of the steam disappears, being 

 precipitated as rapidly as it forms, although the 

 water still continues to boil. 



Artificial Emeralds. — At a recent session of 

 the French Academy of Sciences, Mr. Daubree, in 

 behalf of Messrs. Hautefeuille and Perry, presented 

 an interesting note on the production of emeralds. 

 These learned chemists have succeeded in produc- 

 ing very beautiful crystals of emeralds by fusing 

 silica, alumina and glucina (with traces of oxide of 

 chromium) with acid molybdate of lithia. The ma- 

 terials were heated to a temperature of from 600 to 

 700 deg. for fifteen days. There were obtained fif- 

 teen grams of small crystals about a millimetre in 

 diameter, having all the mineralogical and physical 

 characters of the natural emerald. The longer the 

 operation is continued, the larger the crystals be- 

 come. 



The L.\tent Color of Material. — In a re- 

 cent communication to the Paris Academy of Sci- 

 ences, M. G. Govi has brought forward some inter- 

 esting facts as to the true colors of bodies. In gen- 

 eral, if any substance is illumined by monochro- 

 matic light only, it will appear black, except when 

 the color of the light is the .same as that naturally 

 transmitted or diffused by the material in question. 

 Thus carmine is black when viewed by either green 

 or blue light, ultramarine is black in all but blue 

 light, and similarly with most other colors. Rea- 

 soning from this, it would naturally be concluded 

 that bin-odide of mercury and red lead would appear 

 black, when seen by the sodium light; which is al- 

 most a pure mono-chrome, whilst M. Govi's experi- 

 ments show that in place of darkening, their color 

 becomes a brilliant yellow, losing all trace of its in- 

 itial red. Again, if bin-odide of mercury and vermil- 

 ion, which in ordinary sunlight appear nearly iden- 

 tical, are seen in the sodium ight, the bin-odide be- 

 comes a pale yellow, whilst the vermilion appears 

 brown. M. Govi attributes the above to the fact 

 that the sodium rays are wanting in sunlight, and 

 thus with it the true colors of these bodies do not 

 appear. 



