ANSWERS TO CORRESPONDENTS. All communications should be addressed to the EDITOR of the ENGLISH MECHANIC, 31, Tavistockstreet, Covent Garden, W.C. MORE TESTIMONIES. "The ENGLISH MECHANIC is one of the finest scientific journals of the day, and as an advertising medium it is unequalled."-R. B. SCOTT, Rochdale, April 23, 1870. "I think the ENGLISH MECHANIC is the best paper I ever H. BEVELING.-Thanks. The lines are good, but not appro- C. J. F.-If an illustration or description of your paten' UNEQUAL STEAM PRESSURE.-We have received a long S. F. SHAKESPEARE, of Thrapstone, writes us to say that he 1155 J. H. Johnson. 47. I incoln's-inn-fields, hardening composition, and its employment with india-rubber, gums and oll.-A communication 1156 W. Batchelor, Winchester, improvements in fire-bars 1157. R. P. Beattie, South Castle-street, Edinburgh, improved construction of valve cock. 1158 A. M. Clark, 53, Chancery-la e, improvements in shir fronts and cuffs.-A communication 1159 G. W. Ley, St. John's-road, Croydon, improvements in the production of raised and sunken designs in imitation of carving in wood, ivory, bone, and other materials 1160 R. F. Bigot. Paris, apparatus combining the functions of a bung and of a self-acting vent-peg machines 1163 M. C. Hull, New York, heating stoves or furnaces 1166 J T. Sheppard, Northampton, cutting heel and sole knew to advertise anything of any kind in."-R. ROGERS, Rudge W. R. T.--Answer through the ENGLISH MECHANIC. If pieces or other forms of leather Pottery, Chilmark, Salisbury, April 23, 1870. The following are the initials, &c., of letters to hand up to first post, Friday, April 29: such information is good for one it is good for a thousand. J. T. MURPHY.-For information on Phantom Veloce see THE ENGLISH MECHANIC LIFE-BOAT street, Covent-garden, W.C. Amount previously acknowledged £170 9 10 1107 T. Bell, Walker Iron Works, Northumberland, treating calcined pyrites for the better utilisation thereof 1168 E. Farrington, 63, Grande Rue Passy, Paris, breechloading fire-arms 1169 J. Gray. Uddingston, Lanark, improvements in plonghe 1170 G. T. Bousfield, Loughborough-park, Brixton, mowing and reaping machines.-A communication 1171 J. R. Clark, Maine. U. S. A., machinery for knitting 1172 C. Bardy and L. Dusart, Boulevart de Strasbourg, No. 23. Paris, preparing certain organic bases for producing colouring matters. 1173 J. A. Wade, Kingston-upon-Hull, and J. Cherry, Hornsea, 1174 G. W. Cooke, and H. Kennedy, Bangor, securing ridges of slate or other material to the roofs of buildings 1175 H. Shaw, Newport, Kentucky, U. S. A.. machinery for hulling cotton seeds and separating their kernels from the hulls and fibres 1176 W. Gossage, Widnes, decomposition of certain metallic sulphides, and in the production of alkaline compounds 1177 G. Little, Oldham, combing cotton wool, and other fibrous materials W. T., P. P. W., J. W. P., J. Sharpe, An Amateur, Sergius, T. S. H., who forwarded letter on "Readings from the As a R. R. SCOTT (Rochdale) -For the sixpenny-piece you enclosed Be G. SMITH.-We don't know "J. C. H.'s" address. If you have anything to say, and particularly if you can speak from experience, on the abuse of lunatic asylums, our columns are open to you. URBAN next week. To MILLERS.-In Mr. Sharpe's letter, p. 134, for "saving of HY. SWALLON-No stamps enclosed. No doubt many of our readers would like E. Y The library of the British Museum is free. You must, however, get two householders to recommend you. THE Sixpenny Sale Column is the only place in which can appear queries forwarded by O. C. C., S. H. (Pontefract), R. S. George (Sunderland). T. JONES.-No, we cannot. There is no real remedy but the razor, and we suppose you will hardly care about trying that. Why waste our time and your own in writing about such nonsense? A CONSTANT READER-You may do so without infringing anybody's "rights." J. MOSEDALE.June 4, 1869. In future consult index, and save us trouble of searching. T. J. O'CONNOR.-Hardwicke, 192, Piccadilly, and Groombridge, Paternoster-row. The first is monthly, price 1s. 6d., and the second quarterly, price 29. 6d. C. G-Cannot say. We do not estimate for publishing A YOUNG TYKE.-Yours is only a different manifestation of the same disease. Let your friend apply to any chemist. Third query inserted. CAMBRIDGESHIRE.-Your first two queries have been answered many times. M. L, MOFFATT.-The numbers in the indices refer to the pages. ENTOMOLOGIST. Your queries were answered at some ength in the early numbers of Vol. X. JAMES BELL-Your mention of the can of water experiment shows strongly how people wilfully misinterpret facts. The rest of your letter is simple assertion unsupported by argu 2s. 6d; S. Watson, 28. 63.; Mr. Deekin, 1185 B. J. B. Miils, 35, Southampton-buildings, studs, for 1136 S. C. Lister, Bradford, weaving silk and cotton velvet 1138 E. Hoyle, Bradford, manipulating gold leaf for orna- 1139 M. Nolden, Francfort-on-the-Maine, curing or drying mealy and grainy stuffs, heating, cooling, and mixing fluid substances, and condensing gaseous ones 1140 D. Sowden and R. C. Stephenson, Bradford, boring, 1141 W. Brown, Portsmouth, improvements in the construc- 1143 W. R. Lake, Southampton-buildings, cartridges for 1144 G,Symes, Goding-street, Vauxhall, andJ.W.¡Young, Port- G. W. Elliott, Chesterfield, improvements in slide valves 1180 C. Lungley, Greenwich, manufacture and in the securing of tubes, taps, and plugs in boilers and other vessels 1181 T. Feather, Cleckheaton, machinery employed in slub bing, drawing, and finishing worsted and other fibres 1182 G. Bernhardt, Radcliffe, machines for spinning and doubling fibrous materials 1183 C. H. Savory and W. R. Barker, New Bond-street. apparatus for effecting fumigation, vaporisation, and inhalation 1184 J. P. Ferris and E. Craddock, Gresham-street, London, portable apparatus for generating illuminating gas 1185 L. C. Schermerhorn and C. Schermerhorn, Derby, appar tus for manufacturing cheese 1186 P Spence, production of prussiate of potash, prussiate of soda, and prussian blue 1187 M. Brown-Westhead, Manchester, and machinery for plaiting or folding tapes and other narrow R. Smith, fabrics. 1188 M. Bayliss, Cannon-street, London, manufacture of spikes 1189 W. Thompson and T. Stather, mills for grinding cattle food and other materials 1190 A. Morand, Leeds, kilns or ovens 1191 S. D. Tillman, Jersey city, Hudson, New Jersey. U. S. A., improvements in boilers, air heaters, steam condensers, aud analogous constructions 1192 G. Fenwick, Gateshead-on-Tyne, ropes or cables to be used for telegraphic or other purposes 1193 F. D. Sutherland, King William-street, London, travelling bags and portmanteaus 1194 E. L. Parker, Birmingham, improvements in buckles or fastenings for braces 1195 J. Lord, Crawshaw Booth, J, Gresty, Manchester, and C. Cross, Pendleton, apparatus for separating and sorting cotton 1196 S. Randall, Linsdale, and J. Randall, Stevenage, consoruction of harrows 1197 G. J. Firmin, 19 Lorn-road, North Brixton, self-registering water or liquid gauges 1198 L, Wray, Ramsgate, apparatus for drushing ores PATENTS SEALED. 8081 C. A. Ofverberg, filters and filtering apparatus.-A communication 3098 J. Lockwood, couplings for railway engines, carriages, and waggons 3099 W. Blackett Haigh, circular saw benches 3100 J. S. Grierson and R. Philips, bronzing, colouring, and illuminating cards and paper 3105 J. P. Rennoldson, steam lubricators 3104 J, Dodge, apparatus for forging or shaping metals 3107 T. Briggs, materials used for packing 3110 W. A. Martin and E. Wylam, fuel-feeding and smokeconsuming apparatus for furnaces 3134 J. James, bending and jointing metallic or other sheets so as to form boxes 3178 A. H. Brandon, motive-power engines, and in the means and mechanism for generating such power.-A communica tion 3198 M. Wilson, improvements in sink traps 3225 G. D. Davis, machinery for working rudders 3291 F. Clark, manufacture or pipes, bricks, tiles, and other articles from clay 3339 W. N. MacCartney, improved railway carriage for passengers. A communication 3403 F. W. Webb, improvements in locomotive and other steam engines and boilers 163 J. Dewar, treatment of certain substances for manure 260 J. Dewar, treatment of certain substances for food and for manure 415 W. R. Lake, apparatus for drying sugar.-A communication 419 B. Looker, construction of horticultural structures, cases or enclosed spaces 601 H. Hayward, manufacture of yarns and fabrios containing horse-hair 619 J. Allmann, machinery for dressing or sifting ground wheat or other grain-A communication the use of children 3111 A. Bowater, rolling or shaping metals 3116 T. Clark, improved implements adapted for constructing tube wells and driving hollow piles 3138 W. W. Girdwood, self-lubricating metallic elastic packing 3138 T. Taylor and J. W. Davies, apparatus for singeing horses 3147 E. H. Monckton, improvements in electricity and means of telegraphing 3152 J. U. Mewburn, improvements in apparatus for feeding boilers, and for raising and forcing fluids generally.-A communication 3171 P. Jensen, guns for bayonet drill.-A communication 8412 L. Mount. apparatus for "alling" match splints or other splints $491 J. H. Johnson, spring mattresses.-A communication 3522 D. Prideaux, purifying and calcining gas and soap limes 58 R. Morris and M. D. Penney, treating shoddy and other animal waste to obtain ammonia and salts of ammonia therefrom The English Mechanic AND MIRROR OF SCIENCE AND ART. ANCIENT COINS.-I. BY HENRY W. HENFREY. Tis impossible to estimate too highly the great history. Their influence extends to the remotest ages, and the remotest countries, and they are undoubtedly the most veracious and imperish able of historical records. "I soon pereeived," Sys Admiral Smyth, "the mischievous error of the too general opinion, that an acquaintance with ancient coins is more the province of the antiquary than of the scholar, that it was of little permanent advantage to the general reader, and that it was useless to him whose avocations in life admit of but brief intervals for literary researches. My conviction, on the contrary, showed that without these infallible vouchers, independent of their intimate connexion with the fine arts, there cannot be a clear understanding of many customs, offices, and historical events; that an experimental acquaintance with medals is a higher advantage than the ignorant will admit it to be; and that no one can be disparaged by a pursuit which engaged the attention of and enrolled among its votaries such men as Alfred, Cromwell, Napoleon, Selden, Wren, Canova, Camden, Evelyn, and Chantrey. Look ing backwards to antiquity is not at all going back to it; but the process inculcates various and invaluable cautionary lessons." of the chalkos. Gold was first coined in Greece Samaritan letters:-"Shekel of Israel." Revers, The workmanship of Greek coins was at first very rude and barbarous, but it gradually improved until, about 500 B.C., it had attained some degree of excellence. But the most beautiful specimens of numismatic art belong to the century extending from 450 to 350 B.C. The coins of Athens are perhaps some of the most famous, and the most remarkable symbol on them is an owl. Pieces of Rhodes have the flowers of the pomegranate, Corinth, a pegasus or winged horse; Argos, a wolf's head; Boeotia, labyrinth; Pharsalia, a horse's head; Marseilles, Sicily, three legs joined; Thessaly, a horse, &c. a lion; Peloponnesus, a tortoise; Scio, a sphinx ; A bull on Greek coins is supposed to be the symbol of a river. The most ancient Greek coins are those coined by cities, many of them having been struck before those of the Macedonian kings-the earliest princes who coined money. These civic coins generally have on the obverse the head of the genius of the city, or some favourite deity, while the reverse usually bears some symbol used by the city. The inscription contains the initials, Pinkerton remarks, "Some conoisseurs prefer monogram, or the complete name of the city. the regal coins of Greece, others the civic. The former interest by their portraits, the latter by their variety. The former are more important perhaps to ancient history, the latter to ancient geography. To him who is fond of ancient geography, the civic coins are singularly interesting. It is also pleasing to see ancient accounts of cities, of their customs, religion, and the like, confirmed by the coins." The monarchic coins of Greece are usually very iike the civic, except that they generally have the head of the King on the obverse; and a figure of some god or goddess on the reverse, with the name of the prince. Amongst the Great are very fine, and his tetradrachms and Macedonian series the coins of Alexander the drachms are of common occurrence. The engraving No. 2, represents a tetra No. 2. ΣΙΔΕ We now purpose to give a few particulars of the most interesting coins in the several series, commencing with the Greek, as being the most ancient. The earliest of these were struck in the island of Egina in the seventh century B.C. They have a tortoise or turtle on one side, and square indented marks on the other. In shape they are thick and globulous, being struck out of a bullet-shaped piece of silver, in order to assist the high relief. The different denominations of the Grecian silver coins were the drachma or drachm, the eighth part of an ounce, worth about 9d.; the didrachm, or double drachm, worth 1s. 6d. ; the tridrachm (very rare), or piece of three drachms, worth 2s. 3d. ; and the tetradrachm, or piece of four drachms, worth about 3s. of our money. There are many divisions of the drachma which it is not necessary to notice here in detail, but they consisted drachm of Lysimachus, King of Thrace, bearing of the obolus and its multiples and divisions. on the obverse the head of Alexander the The coins of the Lydians are next to those of Great as a young Jupiter Ammon. The coins Egina in antiquity, and to these succeed the of Alexander himself seldom, if ever, have his gold and silver Darics of the Persians. portrait. These Darics, struck under Cyrus or his nearer successors, are the pieces mentioned under the name of drams in the Bible, Chronicles, xxix. 7; Ezra, ii. 69, viii. 27; Nehemiah, vii. 70, 71, 72. They were current in Palestine in the period after the return from Babylon. The Darics which now exist are thick pieces of pure gold, weighing about 128 grains troy; and bear obverse, the figure of a King of Persia kneeling with a bow and javelin, or a bow and a dagger; reverse, an irregular sunken square. See the engraving No. 1. The later Greek coins struck under the Roman dominion, and having a Roman emperor's bust on the obverse, are called Imperial Greek coins. Ancient coins also exist of kings of Sicily, No. 3. The half-shekels in silver are exactly similar except that they are rather smaller in size, and have the words Half Shekel" instead of "Shekel of Israel," on the obverse. There are coins dated "Year 4," and of very similar design, undoubtedly belonging to the same series as the silver shekels and half-shekels. Copper coins are also assigned to John Hyrcanus, high priest, B.C. 135-106; Aristobulus and Antigonus, B.C. 106-105; Alexander Queen Alexandra, B.C. 78-69; Antigonus, high Janneus, high priest and king, B.C. 105-78; priest, B.C. 40-37. The common type of the obverse is the name of the prince within a wreath; and of the reverse, two cornucopie united, &c. The farthings spoken of in the New Testament were the quadrans and the assarion, small copper coins worth abcut a farthing. The mite was half one of these. Coins exist in brass (or copper) of Herod the Great, and his successors Herod Agrippa I. and Herod Agrippa II. There are also some small copper pieces struck at the time of the revolt of the Jews which ended in the destruction of Jerusalem by Titus, A.D. 70. They have a vine leaf and stalk on one side, and a vase on the other. The last Jewish coins are silver shekels and THE HE case with which the three primary colour appear to be distinguished by the colourblind, is greatest for yellow and least for red. Yellow, blue, and red is the order in which they are most easily distinguished, and we believe no case is reported in which yellow was the colour concerning which the greatest number of mistakes was made. Blue, when well illuminate !, well seen, and some of the colour-blind assert that that is the colour which they can see best, It may be interesting to give here some and yet when blue and yellow are mixed, and form account of the Jewish coins mentioned in the Bible. The earliest are shekels and half-shekels green, the number of mistakes is greatly increased, in silver, weighing on the average 220 grains some mistaking it for blue, and the majority for troy for the former, and 110 for the latter. red, and occasionally for yellow. When Dalton They are generally believed to have been coined first wore the scarlet robes, on his accession to the by Simon the Maccabee, on receiving the per- dignity of D.C.L., he compared it in colour to the mission of Antiochus VII., king of Syria about leaves of the trees; for him there was no distinc140 B.C., to coin money with his own stamp. tion, and in almost every famous case of colourSee the Apocrypha, 1st book of Maccabees, xv. 6. The shekels have obverse, a vase, usually blindness the same two colours have been conbelieved to be the pot of mamma; above it is founded. Troughton, the optician, saw no differthe date in Samaritan characters, "Year 1," ence between the petals and leaves of plants. Year 2," or "Year 3." These signify the Red is the greatest puzzle to those who conyears of Simon's pontificate, the first one being found colours. To some, ike Dalton, it has posequivalent to B.C. 143. Circumscription in tively no existence, others occasionally see it, but As in all the cases we have mentioned the symptoms of colour-blindness displayed them selves at a very early age in each subject, it is not absurd to suppose that the defect was congenital, but there is one notice on record where colour-blindness was the result of injuries received from an accident, and this circumstance is of the highest importance, as it points out the probability of pathological inquiry revealing the true cause of colour-blindness, and eventually teaching to scientific men its successful remedy. This gentleman, a surgeon himself, had been thrown from his horse, and sustained a concus sion of the brain, and there can be little doubt but that to this circumstance is to be traced the insensibility to colour that the eye of this gentleman ever after retained. as often confound it with green. It is a very When Dr. K. refers to the infusion of red cab- fessor Subeck found five out of 10 youths, who comcurious sight to submit different shades of red bage being darkened by alkalies, he unwillingly posed the two upper classes in a gymnasium at Berand green wool to colour-blind persons, and ask furnishes proof as well as statement of his colour lin, to be colour-blind. Professor Pierre Prevost them to arrange the wools according to their dif- blindness, for the infusion which is originally declared that the colour-blind amount to 1 in 20, and ferent colours and shades. Some will lay them purple is not deepened in tone, but absolutely Professor Wartmann did not think that the last out in one sin yow, attending with great nicety, changed in tint to a bright green. Dr. Y. says estimate was a great exaggeration, for he say-, apparently, rrespective brightness of colour; red cabbages growing, pickled, or in infusion, are "I have readily found a number of persons af. we says! itly, for it is not easy for a normal the most beautiful blues I can imagine, and it was fected with this singular anomaly." The care eye to ude whether a shade of full green is by not observing any change by acids in the infu- fully-conducted, and much more widely-extended darker or lighter than a shade of full red. Some sion of red cabbage, when attending the chemical examination of Dr. Wilson is the most reliable will make two distinct bundles, in which the reds class, where I used to stare for the whole hour, with which we are acquainted. The total number and greens will be about equally divided, but expecting to see the change, that I first became examined was 115f, principally soldiers and possibly the most amusing sight is to see a person aware of my great defect. The author of these members of the police force. Of these 1154, 21 debating whether a brilliant red shall be placed papers had his attention first called to the inea- confounded red with green; 19, brown with along with a bright green, and possibly when he has pacity, in certain individuals, of detecting colour green; 25, blue with green. The total number guessed right, for he has no certainty, he will be by noticing that a gentleman to whom he was to some extent colour-blind was therefore 65, or unsatisfied with the assortment, and transfer the showing, in a large refracting telescope, the beau- 56 per cent., which gives 1 in every 17·7 persons red to the green bundle. In many cases an arti-tiful pair of stars that compose ẞ Cygni, saw no as marked with this extraordinary anomalous ficial light will enable one who confounds colours difference in colour between the two, and com- vision. For my own part I think it probable to see them as they appear to a normal eye, and pared them both to the colour of the top part of a that the number of persons in this country as if the assorted bundles of red and green wool be gas flame. Any person with a normal eye that has markedly colour-blind as Dalton was-i.e., given laid before them by candle light, their mistakes seen these two strongly coloured stars, will own to mistake red for green, brown for green, purple are in some cases evident to themselves, when that this gentleman presented a strongly deve- for blue, and occasionally even red for black, is their disappointment is sufficiently aggravating. loped case of colour-blindness, and there can be not less than 1 in 50; and including all kinds and Green and red being such stumbling blocks, it is little doubt but that a personal equation exists in various degrees of colour-blindness, 1 in 20." not surprising that the more composite colours in chromatics as certainly as it does in time, though We are not able to offer any statistics having referwhich green and red enter in combination, should numerous circumstances render it difficult to arrive ence to observations as to colour-blindness made in prove equally ambiguous to a colour-blind eye. at the exact amount of correction that ought to any other part of the world, but it seems not unPurple is taken for blue, the red not being de- be applied to observers' opinions of colour to re-reasonable to suppose that in a country where numtected; orange for yellow, olive for brown, and duce them to a uniform standard. The study of bers are obliged to follow occupations which do not so on. A gentleman communicated to Dr. Wilson sidereal chromatics requires a very correct eye give full exercise to the external senses, the keenthe following account of his own peculiarities of for colour, and the correct determination of colour ness of perception may not be so great as in counvision:-"As far as I can tell, the following ex- of stars affords a most convincing proof of the tries where the senses are more eagerly trained. presses my experience as to colours. Yellow is entire absence of anything approaching to the The susceptibility of the inhabitants of the higher the far brightest colour, blue nearly as bright; phenomenon that we have attempted to describe latitudes to colours is far inferior to that of the these are the only two I see distinctly in the rain- in this paper; to those who are interested in this race who produce the magic dyes of India, or the bow. Ed I can distinguish when bright, but particular study, we recommend Admiral Smyth's still nobler one that built the glowing walls of the other shades I confound with stone colour or grey. work on "Sidereal Chromatics." Alhambra. Even our neighbours the French Green I have no distinct conception of, according excel us in this matter, and it is not perhaps to its different shades it appears black, brown, red, saying too much to assert that most of the yellow, blue, and grey. I cannot distinguish at civilised, and even the barbarian people, excel us any distance the ripe cherries on a tree, or strawin a taste for colours. berries from their leaves. The flowers on the Before we conclude these few remarks on scarlet geranium I cannot see distinctly at a disDaltonism, or colour-blindness, or whatever name Sance by daylight, but by candle light there is a the reader may give this peculiarity, it is desirable marked difference between them and the leaves. that we mention a few of the causes that have I have no conception of what is meant by combeen assigned by medical and scientific men to plementary colours, or of the agreement of account for the defect, and, perhaps, first of all, will different colours when blended together, as, for arise the question whether the peculiarity is to be instance, what kind of a carpet accords with red traced to the physical formation of the eye, and curtains in a room. With regard to my want of whether the simple inspection of the organ could perception of green, it appears to me that the blue decide whether a person was a sufferer from and the yellow hues neutralise each other, and colour-blindness or not. And here possibly would, in equal proportions, constitute what is opinions will differ according to the sentiments of really no colour, varying from a drab or grey to a the readers, and if he be a phrenologist he may dingy black. When the blue rays predominate It will not have escaped the attention of the decide that a knowledge of that science (some It appears blue drab, and when the yellow rays careful reader that in every case mentioned but perhaps will object to the term science) is sufficient are in excess, it appears a yellow drab. When one, the subject of colour-blindness has been a to recognise an abnormal eye. One of the acthe blue and yellow are proportionately blended, male. He will naturally be led to inquire whe-counts that we have partly quoted, and whose as in a lady's green silk dress, it appears to be ther the defect does not make its appearance in length did not permit of the entire recital, adds very similar, and no more colour than a drab silk. females. That there are cases of colour-blindness the following testimony in favour of phrenology: The dry dirt of the street I should equally sup- to be met with in the "softer sex" is undoubtedly "The only fact which somewhat staggered me pose to be green. I also confound red and brown the fact, but the instances are much rarer, and relative to phrenology was that a phrenologist, frequently. I cannot distinguish between treacle when they do occur, the ingenuity of the unhappy then unknown to me, now a valued friend, asked and blood spilt in the street, by daylight, though subject is exerted to its fullest extent to keep the me one day to answer him candidly whether I I believe I could by candle-light." This pecu- defect from being noticed. Dr. Wilson, in care- knew colour, as in me the bump of colour was liarity of vision is best shown by giving the expe- fully prosecuted inquiries for a term of nine absent. Several phrenologists who have seen my rience of those who have been the sufferers from months, discovered only six cases, and had the head since have agreed as to the absence of the it, and as these narratives may be the most in- opportunity of examining but one. The unwil- so-called bump." The only case in which a colourterasting portion of our paper to the majority of lingness that ladies have to confess their inabi-blind eye has been submitted to a post-mortem your readers, we shall make no scruple nor apology lity to detect shades of colours makes the rarity examination (so far as we are aware, with the for extracting such remarks from other cases as appear greater than is really the case, as we be- exception of some general observations by Mr. shall best serve our purpose. Dr. K. gives an fore hinted, and Dr. Wilson notices that women White Cooper), was that of Dalton, at which Mr. interesting account of his confusion of colours, of the better class, who had to make purchases Bally, formerly assistant to Dr. Spurzheim, was but it is too long for complete insertion "Blue where the defect might be noticed, usually present, and took casts of several parts of the and yellow," says he, "are the brightest colours. brought a friend with them to avoid detection. In brain and skull. "He (Mr. Bally) pointed out a Red, that is scarlet, is a pleasing sober colour, arriving at any accurate statistics with reference remarkable prominence on the frontal portion of which refreshes my eye as much as green; indeed, to women, a great difficulty is felt in meeting the orbitar plates (which represents the phrenoI cannot tell any difference between certain shades with large bodies of women together, who can be logical site of the organ of colour, and the imperof these. Red sealing wax and grass, for instance, submitted to a trial. This defect is supplied with fect or deficient development of the convolution are absolutely the same exact colour. Prussian men by examining a section of the army or police of the anterior lobes, which rested upon them. blue and red have the same hue. The rose, the force, or any other body of men, but except in the Of course Mr. Bally adopted this as the true exlips, a ruddy complexion, and the face of a man case of factory girls (whose want of education planation of the peculiarity of Dalton's vision; discoloured by nitrate of si ver, are to my eyes and we as witnesses not only without faith in absolutely the same. Red-hot coals and gamboge phrenology, but even opponents, are bound to yellow are to me identical in colour. Infusion of record the fact." But although we have arranged cod cabbage, deepened by alkalies, or reddened by these two cases side by side, as being prominently acids, to me exhibits no change of colour, only a marked out by phrenologists, as establishing their greater intensity or deeper colour; the actual theory, there is in reality no connection between colour remains absolutely the same. I cannot them, for those who have seen Dalton's bust, by detect cherries or strawberries from the leaves, Chantrey, will see that the superciliary ridge is but by their form. In purchases I have made projected very markedly, so as to overhang the many mistakes; for instance, I purchased a red eyes, and would have been selected by phrenoIress thinking it a green one. I have on more logists as a sign of the possession of an exquisite than one occasion bought red and green trousers, thinking they were brown, and had to get them 1yed afterwards to get them worn. In Paris I bought a red cap thinking it a green one; in fact 3 could give many instances of similar mistakes." renders them peculiarly unfitted for a trial of this Dalton was the first to attempt to inquire what sense of colour. (To be concluded next week.) "Taylor's Scieutide Mem ars, 186. This number includes 130 of Professor Kelland's pupils, examined by that gentleman. Dr. G. Wilson, Op. Cit. insensible at a distance; II. Attraction sensible at a distance. The first class contains attraction of composition, or chemical attraction; attraction of cohesion, the force by which the particles of a body hold together, or, as it is commonly called, "molecular attraction;" attraction of adhesion, the force which unites separate bodies of the same or different natures. The second class comprises electrical and magnetic attraction, and the attraction: attraction of gravitation. Chemical, electrical, and magnetic attraction are studied in their own treatises; "mechanics" deals with attraction of cohesion, adhesion, and gravitation. No. I.-Laws.-The three sorts of attraction are included in one set of Laws. Law I. Cohesion exists in all bodies. Solids, liquids, and even gases, have a force by which their particles are held together. That which is clearly seen in the solid state exists in the other state, though very much diminished. Law II. Cohesion varies in different bodies, and in the different states of the same bodies. It is more in some solids than in others, and diminishes as the solid passes to the liquid and gaseous state. Law III. Adhesion may be observed between bodies in all states. Solids adhere to solids, to liquids, to gases; liquids to liquids and gases; even perhaps gases to gases. Law IV. All bodies attract one another. It may not be perceived by an effect of motion, but the effort at motion exists, between the greatest and smallest. = N B. 1. Law V. Attraction of gravitation is inversely as the square of the distance. In formula, G D'2 (G gravitation, D distance); G D. This fractional form of proportion will always be used, and will be found, after a little custom, to be very convenient. 2. The letters with a dash (G' D') will always signify the subject matter in other conditions. Thus here G' D' signify either the gravitation of a second body at its own distance, or that of the same body, at a new distance. The full expression contained in the formula is, the gravity of one body is to the gravity of another as the square of the distance of the second is to the square of the distance of the first; or, the gravitation of a body in one position, is to the gravitation in a second position, as the square of the distance of the second position is to the. square of the distance of the first. And this, be it said once for all, is the method of formulising "inverse proportion." Law VI. Gravitation is directly proportional G M to the mass of matter. In formula the G' M' gravity of one body is to the gravity of another as the mass of matter of the first is to the mass of matter of the second. No. II.-Proofs.-Almost all these laws admit of experimental proof. Some proofs, however, are not what are called class experiments. Law I. That solids have their particles cohering requires no proof. Liquids: A rod of glass dipped into melted glue, water, or spirit, lifts from each a drop, smaller as the perfect liquid state is approached. These drops consist of particles held together by cohesion. In gases there is such a predominance of an opposite force, that it is not easy to prove the existence of cohesion; yet analogy to the other states seems to require it, of course in a very diminished condition; and the ease with which the heavy visible gases can be drawn about, so to speak, almost proves what analogy suggests. Law II. Between solid and solids. Two plates of metal, glass, &, ground very smooth and level, will adhere without any intermediate body. It is commonly stated that two bits of a bullet made smooth will cohere; or, two FIG. 19 bullets, a part of each being removed, when well pressed together, will bear a considerable weight, even as much as 201b. weight. This experiment was first shown by Triewald. Wax may be used, but it is not so convincing. Between solids and liquids. The glass rod lifts the liquid (Law I.) by means of their mutual adhesion. But there is an experiment, said to be Taylor's, and celebrated for the controversy to which it gave rise, which affords a very convincing proof. To one of the pans of a balance is hung a flat disc. By weight in the opposite pan, equilibrium is restored. Press the disc down gently to a tray of water underneath; remove the hand, the disc, and with it the balance arm is held down by the adhesion of the water and the disc, Fig. 19. A considerable increase of weight in the opposite pan is required to raise the disc. The increase of weight varies with the liquid; it is less as the fluidity is more perfect. When the disc is forced gently up, the cohesion of the liquid state is well seen. The water is drawn up in a hollowed form, Fig. 20, FIG. 21 FIG. 22 growing thinner as the disc rises. Between solid and gases. Into a deep receiver of glass, Fig. 21, is passed down by means of a wire a leaden capsule filled with large shells of Set granulated zine. So. the receiver aside in a quiet room for a day or The zine decomposes the water slowly (a little acid might be added to quicken the action). After some of time the shells zinc will be seen covered with shining bubbles of gas, which, though under considerable water pressure, forcing them up, still adhere to the solid, A slight shock to the capsule raise it a little and strike it against the bottomproduces a beau iful "shower" up of silverlike bubbles, Fig. 22. Left quiet again for an hour or two, bubbles of gas will be again found on the zinc. Between liquids and liquids. A tube of glass wet with water, dipped into oil, will which is in water, and gases in general "in solntion," as it is called, may be said to be in part retained by the adhesion of gases and liquids for it is well known that in aërated liquids the FIG. 20 gas can to a great extent be liberated without any change of pressure. For instance-by stirring soda water, champagne, &c., with a bit of bread, the gas will be freed. As to gases, and gases perhaps, the law of "perfect mixture" However, the may be caused by adhesion. nature of the gaseous state does not seem to require that help to the action of Berthollet's law. Law IV, being Newton's great discovery, and serving in his hands to explain all the difficulties, and remove all the absurd and contradictory notions regarding the system of the universe, ought to be more than sufficient to establish its truth. However, this is not all. It has been proved in two ways. The first was an accidental result-the second by means of an apparatus constructed in part specially for the purpose. The accidental discovery was made in Peru, where some French philosophers were carrying ont a series of astronomical observations at either side of Chimborazo. They found, on comparing results, that their instruments pointed differently at their respective sides of the mountain. The "pointing" of the instruments was controlled by a line with a small weight hung to it. Since, then, the instruments pointed differently, the position of the line must be different. The cause assigned was that the mountain attracted the weight, and consequently gave a different pointing. The astronomical observation required was the "zenith distance " of a star-i.e., the distance of a star from a point vertical to the observer; Fig. 23 (S) a true Law II. The great difference of force required to separate the particles of different bodies. The strongest man cannot pull asunder a small cylinder of iron; the weakest boy can pull asunder a cylinder of elder pith. Lead in the solid state is strong in cohesion; in the liquid it is not much more than water, Water in the solid state withdraw some of the oil, although these zenith distance. The instruments guided by the as ice bolds together well; as steam it has but liquids are usually held to be repulsive one of the questionable cohesion of a gas. the other. Between liquids and gases. The air line and weight made it Sb at one side, and Se at the other. This remarkable fact having cansed (Continued from page 146.) NOW, remarkable as all this is, it is in its lead FIG.7 HYDROGEN ing features by no means new. Nearly 120 years ago Melville observed the yellow tint com-flame which, while tremendously hot, emits consists of red, orange, yellow, green, blue, indigo, with great rapidity, and, consequently, to give a which, starting from the least refrangible end, municated to flame by soda, and Sir David Brew- scarcely any light at all. The great advantage and violet rays, successively melting into each ster revived this idea in 1822 in his invention of this arrangement will be evident when we re- other without break or interruption of any sort or of the monochromatic lamp. Nay, Sir John flect that in dissolving various substances in description. Then we have seen that if we Herschel, in the same year, instituted experiments alcohol (or spirits of wine) and burning that, examine the light of an incandescent gas or when we examine the resulting flame with our vapour, on the spectra of various substances, and notably prism, we not only get the spectrum of the dis- tinuous spectrum, but one of rays of relatively we no longer find it yielding a conof strontium and of the chlorides of copper; and solved substance, but that of the burning alcohol few degrees of refrangibility; so that in regardin his "Treatise on Light,” in the " Encyclopædia as well, thus complicating the observed appearing a narrow slit illuminated by such light, Metropolitana," Vol. 4, published in 1827, says :- ance in a very perplexing way. On the other through a prism, we obtain a spectrum consisting "The colours thus communicated by the dif- hand, with the fiercely hot, but scarcely luminous of bright lines in various parts of the solar specferent buses to flame, afford in many cases a flame of the Bunsen burner, we get practically trum, but separated by intervals of total darkness. ready and neat way of detecting extremely minute nothing but the incandescent vapour of the Lastly, we have the discovery of Wollaston, or particular substance which we may have under perhaps rather of Fraunhofer, that the Solar quantities of them." Among the names of those examination. Employing, then, this simple and Spectrum is crossed by a series of stripes, lines, or who pursued this curious train of investigation, ingenious apparatus, in conjunction with their shadows, whose places in it are fixed and inwe find, too, the honoured one of Fox Talbot-spectroscope, Kirchhoff and Bünsen soon convin- variable; that these lines are seen in all light perhaps better known as the practical originator ced themselves that "the most different salts of derived directly or indirectly from the Sun, such of photography in England, and the inventor of the same metal, if they are volatile, produce the as that of the day sky, the moon, the planets, same bright lines in the spectrum, but with different &c., and that although some of the dark lines the Talbotype; and he, albeit erring in his degrees of brilliancy; and that a mixture of salts pertaining to sunlight are found in certain of the determination of the elements to which certain of different metals gives a spectrum similar to fixed stars, yet that others are absent. We stated lines were referable (and notably with regard to that which would be produced by a superposition on p. 116 that Fraunhofer had mapped between the yellow line of sodium, of which we have pre- of the several spectra of the individual metals." 5 and 600 of these lines. We may here add that viously spoken, and which he attributed to In his original memoir, Kirchhoff, after speaking more recently Kirchhoff and Angström have inwater!), yet points out clearly how the spectra of the recognition of the lines of the several metals creased the number to very many hundreds, of particular elements supply unerring means under varying circumstances of their production, some of them being of the very last degree of of deciding what those elements are. Next, as goes on to say-and this is of the very greatest faintness. we approach our own time, we find Professor W. possible importance-"The dark lines of the solar A. Miller, F.R.S. (whom we shall by-and-bye spectrum afford invaluable assistance in determinhave to speak of as the associate of that emi-ing the position of the bright lines of the elemennent astronomical sprectroscopist, Mr. William Huggins, F.R.S., iu his researches on the chemical constitution of the heavenly bodies) pursuing investigations into the spectra of the metals of the alkaline earths. Then, in 1857, Swan showed conclusively how the single yellow line which we have mentioned above was produced by sodium; and how, moreover, this element was everywhere present in earth, air, and sea; so that, light our lamp where we may, it is almost with a moral certainty that the combustion of sodium will at once commence. a In figures 5 6 and 7 we have endeavoured to give some faint pictorial idea of what we have been describing; but it is obviously impossible to reproduce in black and white upon a wood block the chromatic phenomena exhibited. Fig. 5 is intended for the Solar Spectrum; Fig 6 for that of Sodium; and Fig. 7 for that of Hydrogen. Well, then, in 1814, Fraunhöfer discovered that when he got the spectrum of the Sun (Fig. 5), and the spectrum of Sodium (Fig. 6), into the field of his telescope together, the dark line which he lettered D, and the yellow line of sodium, were coincident, each appearing as the mere prolongation of the other; and in 1849, the great French physicist Foucault, noticed, on passing direct solar light through the vapour of sodium that the dark line D came out in the spectrum of the Sun with startling distinctness. tary bodies." He then proceeds to describe an arrangement entirely similar in principle to that illustrated in Figs. 2 and 3, and observes-“In this way, whilst in the upper half of the field of the (astronomical) telescope, the solar spectrum is seen, in the lower half, but in immediate contact with the other, the spectrum of the artificial source of light becomes apparent, and the positions of the bright lines in the latter spectrum can be accurately compared with those of the dark lines in the solar spectrum. In order to obtain the spectra of the metals, I have almost It is, however, to two German philosophers, invariably employed the electric spark, chiefly Büusen and Kirchhoff, that we may be said to owing to its great luminous intensity." To this owe spectrum analysis in the form in which we we may add that the spectrum of any body gaseous uow possess that most potent addition to chemical under ordinary condition, such as carbonic acid, These facts, however, remained barren until 1859, science. Commencing their experiments on the hydrogen or nitrogen, is obtained by the passage when Kirchhoff and Bünsen began their investispectra of the metals, some year or two of the electric spark through the gas under ex-gations, which eventually led to such surprising alter the period at which Professor Swan amination, which is itself sealed up in a glass results, and the exceeding importance of was at work on the subject, they, in their labora- tube; and that even to the naked eye, the differ- Kirchhoff's crucial experiment is such that we tory at Heidelberg, gradually built up, on ence of colour presented by the spark is most will give his account of it in his own words: "In solid foundation, that marvellous theory by noticeable, it appearing blue in carbonic acid, red order," he says, "to test in the most direct manner the aid of which we are able to look out into in hydrogen, and yellow in nitrogen. And here, possible the truth of the frequently asserted fact the dim confines of space, and assert that certain although we are slightly anticipating, we cannot for- of the coincidence of the sodium lines with the elements are present in, or absent from, the in- bear to notice that when we examine the spectrum lines D, I obtained a tolerably bright solar finitely distant bodies which tenant it. Let us of this red hydrogen spark we find it to consist of spectrum, and brought a flame coloured by sodium try and follow their reasoning, and see how they merely three bright lines-one red one so bril- vapour in front of the slit. I then saw the dark arrived at so very wonderful a conclusion; albeit liant as almost to overpower the others; one lines D change into bright ones. The flame of a to do this will involve some slight repetition of bright greenish-blue one, and one dark blue, or Bünsen's lamp threw the bright sodium lines upon what we have previously said. As our aim is, almost indigo line, which is naturally not so the solar spectrum with unexpected brilliancy. however, above all things, to secure clearness bright; and that the fact of the most vital im- In order to find out the extent to which the and perspicuity in our explanation, a little reitera-portance in connection with this is that these intensity of the solar spectrum could be increased, tion is unavoidable. without impairing the distinctness of the sodium lines, I allowed the full sunlight to shine through the sodium flame upon the slit, and, to my astonishment, I saw that the dark lines D appeared with an extraordinary degree of clearness. I then exchanged the sunlight for the Drummond's or oxyhydrogen lime-light, which, like that of all incandescent solid or liquid bodies, gives a spectrum containing no dark lines. When this light was allowed to fall hrough a suitable flame coloured by common salt, dark lines were seen in the spectrum in the position of the sodium lines. The same phenomenon was observed if instead of the incande They began, then, by volatilising or vapourising the substances whose spectra they wished to examine by means of what is known as a "Bünsen's gas-lamp," or "Bünsen's burner," the invention of one of the experimenters himself. One form of this is represented in Fig. 4. The gas passes through the supply pipe 8, into a perforated chamber c, where air mixes with it; they both rush up the tube ct, in combination, and the mixture is ignited at t; r represents a ring burner to make a larger circle of flame. This fi's in at t. The effect of this arrangement is to consume the solid carbon particles in the coal gas three lines are found to be absolutely coincident And now, in order that we may comprehend and |