Show from the st james magazine HOW looking GLASSES ARE MADE the essential ingredients for making glass are arc only two sand and sada or sand and potash other ingredients are added but mostly in small quantities according to the sort or quality of glass required thus lime is added to make the mixture melt mo more re easily manganese niang anese and cobalt to im improve its color lead to increase the refractive fr power arsenic to make it white still the only essential ingredients are the sand and soda if the glass is to be good the sand must be pure S c j 35 nearly y u unmixed silex sites as possible good sand comes from lynn and from ra alum kum bay the best of all from tho the forest of fontainebleau Fontain bleau excellent sand gand however good enough for all ordinary purposes comes from the mc ilc dway the soda used by the glassmaker was formerly obtained from burnt seaweeds in this form it was called kelp and was formerly orm e maddon made on a large scale seah 3 in the hebrides as well as on the western coasts of ireland ireland and scotland it was very expensive costing latterly in london as much as 20 a ton for many years however the kelp trade has become almost extinct carbonate of soda kida of much better bette r q quality u allty is now obtained by byr a simple chemical process in any quantity and at a very much cheaper rate from common salt there are few transformations in the whole range of the arts more striking and more beautiful than that which give nive birth to glass A heap of sand and soda it used to be of sand and aidash ashes to look at like common road dust in is changed by the simple application of heat into solid transparent brilliant lass it is even more wonderful I 1 al than i lie transformation of a linnol handful ful fui of dirty rag ra into a sheet of white note i we 0 nye aie nilst first imo ini u ros rol room m or rather tn n ou our house in w which jeh the raw materials tle ih the sand the soda the arsenic ac fee along mono with broken glass or cullet are arc be being ng carefully mixed by hundred weights at a time time the follow following n 9 is 41 to b bagood a good receipt for malting oa piare glass net nev le awl an I 1 lbs lbs Ibs SOO oda lbs ibs 1 lbs 2 lime lbs abs ibs SO 30 oxide aide i xu lugin esc ese coxs 32 ide il cobalt gozs 3 1 allet ibs 3 00 I 1 it cles cies does oles not take long to complete our uz nape te I 1 tion a of this preliminary process and as 11 it stirs up more dust and dirt than are pleasant to nose or eyes or diroa we may go on onto to the furnace room here the heat is tremendous coming from fron vast dome shaped brick furnaces lur naces twenty feet high containing four or six earthen pots apiece in each of which two or three thousand pounds of glass are melting tile the flamo flam of and heat are intensely fierce and yet it lakes from sixteen to eighteen hours of exposure before the mixture melts and six or eight more before the glass is workable these furnaces are often kept burning for weeks to together ether and we have men ken seen one which had had not gone i out for eight years one might wonder how the pots themselves could stand against so intense a heat and in fact one of the most delicate operations in the whole establishment is the manufacture of these pots they are made of stourbridge Stour bridge fire clay and are built up entirely by hand without the help of a wheel ar or lathe much as a swallow builds her nest aest it is found necessary that each additional layer of clay which adds an inch or so to the height of the pot should be quite dry before belore the next is added and as the drying takes place slowly a large number of pots in different stages of completion are always in n hand the workman adds a layer to each one after another and by the time he has gone the whole round the first in iu dry enough to receive received rece ivea a further addition the accuracy with which long practice enables the man to work is so great that the pots appear as truly circular as if made on a wheel but we must return to the furnace room the workmen open a little door in D the furnace and by looking through a smoked glass tas fas as if examining the lui lul in m an eclipse find that the melted las aas alasi 1 is bit fit 1 I for or casting no easy job is it the full of the melted 0 o gel ee pots glass the rii cli ru metal metai etal as it is called out of the burning bunning I 1 i nie fie fiery ry furnace and still less easy to n danage nage them when they are out imael ImaKi imagine nea a gigantic pair of curling tongs tones mounted on wheels brought up to the furna burnaw co door in the blinding glare iare lare of which are only just visible the ghostly forms borins 0 the white hot melting L pots p in a moment the curling tongs have caught one of the tots pots by its middle middie and their grip has been een made firm by a screw then aa as many of the workman as can canis canie tand stand sit or hang on the tho opposite endom end of the tongs by jum jumping p ing and jerking at last lift the pot from its fiery bed and wheel it out in triumph playing at seesaw see saw with it till it gets geta close to the casting table here the tongs deposit their burden on the ground so hot that it almost burns your eyes to look at it and wheel omm off here we must stop a minute to give gire a mance dance at the casting table it is long iong and lind low made of iron and as amos smooth th as iron can be planed at the upper end where the lady of the house would sit were it a dining table is a metal roller say a foot or rather more in diameter ana and and ana some few inches longer than the table is wide along the whole length of the table and at the distance apart art corresponding to the width of the plate plato ato ate to be cast are clamped two parallel ri el iron bars of the exact thickness required for the glass over these as on rails the rollers will run and they will serve to keep the metal within its pr proper oper limits and now though without the dela deia delay y of one tenth of the time that it has taken to read the last paragraph the white hot pot with its fiery contents has been clutched by another pair of curling irons which hang by chains from a crane close by it is then immediately hoisted up and suspended a foot or so so above the table and just in front of the roller the foreman and two or three ef of the men some on one side slide of the table and some on the other take hold of the long handles of the curling irons the pot in this case hanging banging from the centre and gently tilt its contents which look like red hot treacle upon the table the roller is at once set in 1 motion by a windlass and rolls out the glass just as the cook rolls out her paste as lightly and as quickly in a minutes time the sheet of glass large enough for the largest shop window on ludgate hill is so far 0 finished ilni lini shed and the roller drops quietly nto into its bed at the lower end ond of the table instantly for success appears to depend as much upon the speed with which it is 61 di 61 all ali dope done as upon the skill a flat truck as large arwe as the table itself is run up and the t h e sheet of glass still hot and alid sparkling is pushed on to it and car carried ried off to tile the annealing oven where 11 it is left for a day or two to coo cool gradually otherwise it would be so britt brittle brittie leas as to be useless we must not imagine that our pur plate of glass is as yet vet fit for fora a lookingglass looking glass if it were looking glasses would be a great deal cheaper than they are no at this stage of its history our plate is hardly more lore smooth or clear than common norl pond ice we sometimes see glass in in this condition used for skylights and for the roofs of railway stations it lets in a certain amount of ight light but for seeing through is practically opaque let us therefore follow it into the th large elarge wet noisy rooms s where it will be ground and polished the first thin thing done ia is to bed the i plate which haibe maibe may be as much as ten ora or a dozen feet long by six or eight wide on a perfectly level stone table by means of plaster of paris A flat piece triece of wood the size of a small door mat which has flat plates of iron screwed on its under side to make it grind more vigorously works by steam power with a circular motion over the glass plate sand and water are freely supplied to this grinding apparatus and as may be believed there is no resisting such decided measures E even ven the hard stub stubborn born glass is obliged to yield its inequalities and roughness and sharp points are all rubbed down though even when this part of the process is complete it is still far from presenting the polished reflecting ting surface which it gets after a while when both sides have been smoothed in this rough way our plate has to submit to several more some whet similar processes each less severe sever ethan than the preceding one the final degree of smoothness ia 1 imparted by making two ila pla slates t es of glass rub to together ether with the in nest e s emery between t hem them yet still our friend though no longer rough is unpolished he possesses no of reflection and is as dull as a aulice sowers ance one further course of discipline however him from all these defects A long continued brushing by ste steam m power such a fashionable process nowadays now a days though seldom it is to be feared attended by such beneficial results krings brings brings him up to the last pitch of polish and when he has had all his sharp corners and jagged edges trimmed off with a diamond he is fictor nit fit for a mirror for the queens own drawing room but how does our plate becom become a mir mirror 0 r ahat hat gives it its wonderful p powers oe o e rs of re reflection strictly speake speaking ng it is not the glass at all that reflects but bui but the metallic or other surface behind it that spectral reflection which we may often notice overl overlapping tipping the true ima imn imae image e is the only one due to the glass and alyd were it as easy to keep the reflector at the back baek as polished as free from tarnish and aa well protected without the glass aa as with it the glass would not be needed the reflecting surface to farm form a good mirror must not only be perfectly eyen even but must throw back baek as many of the rays that fall upon it from any object and absorb as few of them as possible otherwise the image will be distorted or dark practically illy tily it is found that no sort of mirror answers these conditions so a nearly as plate plato glass with an amalgam of mercury and tinfoil fixed on the back of it for certain delicate purposes as for the reflectors in astronomical instruments or even in the beautiful form of the kaleidoscope the debu scope a mirror all of metal is preferred though even for telescopes reflectors of silvered glass are beginning to be preferred to those made of speculum metal the reflector of the great foucault telescope is made of glass and the abbe meigno speaks of a drawing representing the double nebula in canes Ve natiel ici lei as seen by its means as exhibiting incomparably more details than those given by herschel and lord rosse 11 and yet the diameter of the foucault telescope is less than half that of its rival at Parsons town but for nine hundred and ninety nine nind out of every one thousand mirrors quick silvered glass is made use of we might easily be tempt tempted eel eol to digress into the history and mystery of tin so peculiarly a british product as to have given the most ancient known name to our islands the tation must be resisted nor must we say much about the other substance employed in silvering our glass plate the quicksilver the giving living silver that is bliver silver that runs about as if alive it c comes ines to us principally from almaden in spain idria in carniela Car niola and froni from california and its uses and abuses are numerous barometers are made with it and gold is separated from the crushed ore by means of it the farmer anoints his hig sheep with one preparation of it your butler spoils your plate by cleaning it with another and your doctor half poisons vou you you with a third in our present paper we confine ourselves to its employment by the lookingglass looking glass manufacturer our old friend the plate of glass has been brought to the fic factory tory tony and ands is being diligently cleaned with rottenstone rotten stone and spirit of wine meanwhile on a flat stone table a sheet of tinfoil is laid a little larger than the plate and is surrounded with a low wall made of str strips of glass on this quicksilver is pour poured 19 till it stands at a uniform depth of half an inch and is allowed to remain undisturbed for a few minutes during which time its lower surface is forming an amalgam tinfoil thep the plate ate of glass which probably weighs 1 0 s ve very veny ry many pounds is now careful carefully lifted up and placed with one end of its ts cleansed face flat on the mercury and is then gradually pushed onwards driving before it any impurities that may be floating on the top when the whole glass is thus laid on its mercury bed it is covered all over with heavy weights which squeeze out the excess of metal and in this position things remain undisturbed for twelve hours or more by which time the bright amalgam amalyan has become fixed to the glass in a few days it may be framed according to its T quality size the market it is intended mor for I 1 r or the taste of an individual purchaser and from that time forward may begin making its quiet faithful reflections careless whether they are neglected or improved in common other trades in which mercury is largely used glass silvering is is a very unhealthy business the workmen become subject to a abort sort of paralysis popularly called the trembles or the shakes trembling more or less viol violent accompanies every attempt to use the voluntary muscles the patient dances rather than walks he cannot keep his arms quiet nor direct them at will his speech is hurried and abrupt and in extreme cases he cannot masticate his food sometimes the disease attacks him before he has been more than a few weeks in the manufactory and it is thought wonderful if he escapes a year or two without a seizure the patient usually recovers if he can change his employment for a more healthy one calitr CENTRAL AL PACIFIC RAILROAD goy GOV low of Califor california nik nih in his message says president stanford reports that the company has ample means at its disposal to push forward the work with great rapidity and predicts that the road will be finished and in running order to salt lake early in the year 1869 |