Anoiisi 30, 1877] 



NA TURE 



o77 



Mean = 8-0884 



No. 23 showing an excess over No. 17 of -0154 British units 

 of force, or of -ooig of the whole horizontal force. 



We observe that the greatest value given l)y No. 17 is less 

 than the least value given by No. 23, and infer that the difference 

 between the two means cannot be attributed to probable error of 

 observation, tlie value of which for a single determination (about 

 -ooi of the whole force) is, moreover, much smaller. If we now 

 remove the corrections applied for induction to the vibration 

 observations, the mean value yielded by No. 17 becomes -0004 

 of the whole force greater than the mean yielded by No. 23. It 

 thus appears that a small correction, such as we have already 

 seen reason to expect, is required for the vibration observation, 

 but— on an average for the two instruments employed — only of 

 about one-si.xth of the value of that which it is the custom of 

 magneticians to apply ; and as this small quantity scarcely 

 exceeds the probable error of the mean determination of the 

 horizontal force, it is yet premature to attribute it to any defini:c 

 cause. Whilst, however, the experiments afford no sufficient 

 reason for applying this small correction, they speak very dis- 

 tinctly in favour of no induction correction at all for the vibration 

 observation as against the common practice. 



To show that the error that we have been discussing is not of 

 that minute order that is usually disregarded, we may mention 

 that it would amount, in the case of the unifilar magnetometer 

 used at the Observatory, to about eight times the probable eiror 

 of an observation. 



SECTION B.— Chemical Science. 



Oh (! Nav Mechanical Furnace used in Ihc Alkali Mannfactiirc, 

 and for Calcining Purposes generally, by James Mactear, F.C.y. 

 — The author exhibited and explained the construction of a 

 working model of the furnace which he has introduced for the 

 calcination or so called carbonating of soda, ash, or alkali, and 

 which is also applicable to many other operations, notably that 

 of calcining copper ores, especially as required in that branch of 

 copper manufacture called the " wet process." 



These furnaces are now being widely adopted by alkali 

 manufacturers with great success, the saving in labour having 

 been over 60 per cent., and of coal over 20 per cent., while the 

 quality of the work done is much superior to hand work. 



On an Imprcncd Syslem of Alkali Manufacture, by Mr. James 

 Mactear. —The author described his improved system of manu- 

 facturing blend ash or crude alkali, and claims that it has the 

 following advantages : — 



1. By its use the output of the ftirnaces has been increased 

 from 50 per cent, to 70 per cent. 



2. There is a large saving during the lixiviation and in coal. 



3. There is a much reduced quantity of waste. 



4. There is a considerably increased yield of alkali from a 

 given amount of sulphate of soda. 



5. There is a considerable s.iving in wages. 



The process is now widely adopted in Great Britain, and is 

 also most successfully used in France. 



On the Kegeneratton of the Sulphur employed in the Alkali 

 JSIanitfacture, by the ** Mactear Proeess^*^ as conducted at the 

 works of Messrs. Charles Tcnnant and Co., St. Rollox, by 

 James Mactear, F.C.S. — The author described his process as 

 conducted at Messrs. Tennanl's works, at St. RoKox, and showed 

 how by its adoption the nuisance arising from alkali waste 

 deposits and the drainage therefrom had been removed. He also 

 gave details of the cost of manufacturing sulphur by this process, 

 and a description of the plant employed. 



The " Mactear Process " is specially applicable to those cases 

 >vhsre the drainage of the waste deposits is allowed to flow into 

 streams or rivers, as by collecting the drainage liquor snd 



treating it in the manner described by the author, not only is a 

 great source of nuisance removed, but a nevv outlet is obtained 

 for hydrochloric acid, while the sulphur is produced at a cost 

 which leaves an amply remunerative margin to the manufacturer. 



Messrs, Tennant and Co. now recover weekly about thirty- five 

 tons of refined sulphur by this process. 



The Action of Various Fatty Oils upon Copper, by W. H. 

 Watson. —This communication enumerates a number of experi- 

 ments showing the extent to which different oils act upon copper, 

 the conclusions arrived at being that paraffin and castor oils have 

 the least action upon copper, whilst the action of sperm and 

 seal oil is slight. The rest of the oils examined— linseed, olive, 

 almond, colza, sesame, and neatsfoot, all act considerably upon 

 copper, the action of linseed oil being especially great. The 

 author concludes from experiments that the comparative action 

 of different oils cannot in all cases be decided upon from the 

 appearance of the oils after exposure to copper plates, though 

 minute quantities of the metal may be easily detected in n:o;t 

 oils from the colour produced. 



On Changes in Candles produced by long Exposure to Sea-v)ater, 

 by Prof. Gladstone, F. R.S. — Mr. Latimer Clarke had sent the 

 author some specimens of candles recovered from the wreck of 

 a vessel sunk off the Spanish coast in 1 702, which have remained 

 submerged for a period of 1 73 years. The wick has rotted away, 

 having scarcely any trace of its existence, while the fatty portion 

 has become a friable heavy substance of a dull white colour. 

 The candles bore evidence of having been formed by dipping. 

 The fat may be easily separated from the rest by ether. 



After exhaustion with ether there remained a strongly alkaline 

 white ash, consisting of carbonate and chloride of cilcium and 

 sodium, with traces of potass um and magnesium. From analysis 

 it appears that the fat has been converted in great measuie into 

 calcium and sodium salts, doubtless by the slow replacement of 

 the triatomic group C;,?!^ in the stearine, by three atoms of 

 the metal, with the simultaneous production of glycerine. 

 Though the calcium in sea-water is far less abundant than 

 the sodium, it appears to have had a much greater 

 effect, and it is impossible to say whether the one salt 

 may not have been made by double decomposition from the 

 other. The author pointed out as an interesting point that 

 whereas the fats have been in contact with a practically un- 

 limited quantity of sea- water for 173 yoars, and a chemical 

 change between them has been possible, the double decomposi- 

 tion has proceeded so slowly that the reaction is only about half 

 completed at the present time. 



Contribution to Chemical Dynamics, by C. R. Alder Wright 

 and A. P. Luff. — Guided by certain theoretical .'peculations, 

 the authors are endeavouring to trace out the connections 

 between the chemical habitudes of certain substance; and the 

 temperatures at which their mutual inter-reactions are first notice- 

 able, and notably the relations between the heat developed 

 during their actions and these temperatures of initial action. 

 E.xperimenting on oxides of copper and iron in dilferent condi- 

 tion as to molecular structure, they find, that whilst the initial 

 temperature of action varies within certain limits with the 

 molecular state of the metallic oxide, when they are subjected 

 to the ordinary .-clion of carbon oxide, hydrogen, and carbon, 

 a given form of either oxide is invariably acted on by carbon 

 oxtde at a lower temperature than by hydrogen, and by hydrogen 

 than by carbon ; whilst the heat evolution during the reduction 

 of the metallic oxide by carbon oxide is always greater than that 

 during reduction by hydrogen, which agatn is less than that 

 during reduction by carbon. Similarly, so far as they can be 

 compared, that metallic oxide is acted on at a lower tempera- 

 ture, in the production of which there Is less heat evolution {i.e., 

 in the reduction of which there is most heat evolution). How 

 far these generalisations are applicable to other metals is under 

 examination, as are several other collateial points. 



On the Coal broui;ht Nome by the late Arctic Exf edition, by 

 T. Wills. — The coal occurs on tlie side of a narrow mountain 

 gorge about two miles from Discovery Bay, the winter quarters 

 of H.M.S. Discoi'cry. It appeared in the form of a slight 

 saddleback thickest in the centre, becoming continually smaller 

 at each end ; the thickness of the seam at the deepest visible 

 portion was 25 feet, and its visible length 250 yards ; neither the 

 bottom of the seam nor the underlying strata were visible at any 

 place. Overlying the coal was very triable carbonaceous shale 

 containing impressions of miocene plants, and above this shale 

 a hard fossil red clay stone similar to the red miocene rock of 

 the Disco coal beds, but sterile. The scam is almost iniif^orm in 

 character, and is very free from clayey veins. Onobtain-ng the 



