The California Fairs—How San Francisco Looks to a New Yorker. MESSRS, EDITORS :—Referring again to the Mechanic's Institute Fair, I would remark that although it is almost wholly an exhibition of the productions of this side of the Rocky Mountains, there are not a few articles, mechanical as well as merchantable, brought hither from the busy towns of the most eastern easterly States, So large an assortment of washing machines, for instance, could never be gathered in any part of the world without the help of New England. And so of brick machines, though prominent among these for apparent efficiency, is the “ Climax,'” born, I think, of these west-coast min ds. Two articles there are which pre-eminently represent Cali fornia as we have known and read of it any time these twenty years past'-:'one an ore crusher, with its half dozen heavy pounders almost constantly busy in reducing golden stones to powder; and the other an immense wine cask, capable of contai ni ng something more than four thousand gallons of California's choicest juices. If one of those crusher- pounders were but playing its ponderous t une in th at bi p' barrel, I should be obliged to recall scenes of early youth when the family linen was duly pounded into cleanliness. A very ingenious contrivance in the application of steam to pumping-so much of which is required west of the mountains—is Martin's oscillating engine and pump. Both consist of two cylinders cast in one piece, the two piston heads connected by rods on the outsido. the steam and water being admitted and discharged through the oscillating shaft at the center of the casting. In the same line of improvement, but not like the first, adapted to use for power purposes, is the Wilcox Steam Water Lifter. In this the steam itself acts directly on the water' by means only of an intervening plunger, the steam being admitted at one end and the water at the other end of the same cyl inder.. One of the peculiarities of Californian life, or rather one of the evidences that Californians are fully “ posted up “ in the movements of the day, may be seen in the stands set apart for institutions connected with what are popularly called “Women's Bights..” Among these is a Women's Printing Establishment, w h ore orders are taken, and the work executed and delivered without aid or intervention by the lords of creation. Connected with this are women artists and women engravers, and the eetablishment really covers all the demands made upon it, by th” labor of the fairer sex. Indeed, the artist and wood.engraving department is, as I know, carried into some fine mansions here, and supersedes the useless fancy stitching and embroidery once the only way of killing time among their i nmat es. But it is full time that I left the Fair building and remarked up on the appearance and construction of the city. To how great an extent San Francisco depends upon the neighboring forests can scarcely be realized save by ocular demonstration. Suppose, if you can, that every brick and stone of whatever variety were removed from the great city of New York ! What would remain? Possibly a few buildings of iron and wood ; but would not the city be gone, and its very Bite an unmarked wilderness ? And just so much. and nothing more, would remain of the city of San Francisco if once the wood were removed. Beginning on the ground the street pavements would disappear —not principally Nicolson either, but plain common planks two or three inches thick. After them would go the sidewalks and curbing—then the fancy fencing to door yards, some of which vies with our best iron railings in beauty of design and finish—then the porches, and steps which ap pear to the passeI"' by as the equal in solidity, as in ornament, of those grand entranc'e ways on Fifth avenue. And, lastly, the apparently solid blocks' of sandstone and granite so deftly wrought, imposing in more senses than one—the very body and walls of the house—would melt to nothingness. A few slender brick chimneys and a few heaps of c rum bled plaster might be said to remain sole evidences that a groat city once existed. Next to the construction of the houses the manner of improving the ground is worthy of remark. “ 'Frisco,” as Cali- fornians love to call it, is located on the sid es and at the foot of sand hills. Below, the streets are level and regular, but on the side hill, necessity rules, and the front door of the house is often thirty, if not forty feet above the street. On the street line appears a common stone wall ten to twenty feet high. The wall is rough and ungainly—unpromising to the las,t degree—and the rnde doorway pierced through it, has all the appearance of leading to the kitchen. Ent ering, we rise by successive flights of stairs, and emerg'e upon a delightful parterre of flowers and shrubs. The house stands sufficiently back, -and so en tirely by its elf as to possess nearly all the attractions of a villa in the country, while its windows command the whole city on the plain below, with the blue waters of the bay beyond the distant mountains.B. San Francisco, Sept. 30, 1869. sion, to offer a few suggestions as to what is necessary in order that mechanical appliances may be made to do the work of cotton picking, In the present condition of cotton culture it is necessary that anything that does the gathering shall have an intelligent controlling power to direct, in order to reach the indi vidual bolls without damaging the plant; this cannot be imparted to machinery ; therefore it becomes necessary that the cotton plant itself shall be so improved or modified that the whole of its produce shall be ripened at one time (much more difficult problems have already been solved by horticulturists). and if but one plant out of the many cultivated can be found answering to this requirement it will take but few years to seed this whole continent, then, and not till then, can we expect mechanical ingenuity to assi st in the gathering of the crop.A. D. C. New Madrid, Mo. Setting Work on the Face-Plate of a Lathe and Spacing Circles. MESSRS. EDITORS :—1 beg to offer some practical suggestions on the above subject, where great accuracy is required, which may prove of service to some of your readers. Let the work be set out, and first lightly prick-punched ; then clamp to place lightly as near as possible, but never set the “ dead center “ against the work, for that will not bring it true—now with a “ scratch-awl “ or a sharp-pointed center, with th e point resting in the prick mark, and the other end held against or on the “ dead center,” revolve the work. If the point marked for the center of the hole is out of truth , the “scratch-awl,” or whatever rests in the point, will vibrate. Put into the lathe rjst a tool, without fastening it, and push it up to the scratch as the work is revolved, and the extent of the vibration can be seen. The work can be driven as thus indicated. When there is no vibrat ion of the scratch or center, the work is perfectly set, an d may be secnrely fastened. I regard this as the only perfect way to set w0rk, and yet good workmen (?) take some other way. In you r reply to a corre spondent who seemed to have something for readily spacing a ci rcle, a few weeks ago, I was re min ded of a plan I used successfully years ago. Machine tor Picking Cotton. MESSES. EDITORS :-In your number of July 24th, 13. W. Woodward asks for a cotton picker, but repudiates the tin tub” ch-Rin picket style, l would like with vour permi" ' X ' - I A; \ V : 1 I took a well-seasoned board something wider than the half of any circle I expected to space, and more than twice as long, so as to get the half circle upon it, and drove a bit of hardened steel that was pricked for the center into the center of the circle. I then drew with a sharp knife a line through this point the whole length of the board. This was the diameter, or my starting point, line. I then spaced this half circle with dividers into twelve or any other number of spaces, b eginnin g always at the left, so as to have the spaces right for a whole circle, then with the sharp knife I drew lines from the center through the points spaced on the circle, and numbered them with ink from twelve round to three. I then varnished the board. To use it now, take the dividers, open half the diameter of the circle you wish to space, and with one foot on the steel center touch the first line on the board (chalked so as to mark through the chalk and not deface the board) and then the line numbered for the spaces you wish ; the distance between the lines thus marked was the right distance for that circle in spacing it. The board was subject to atmospheric changes, of course, and so was not perfectly reliable, but sufficiently accurate for a good deal of work in a machine shop when templets could not well be used.WM. L. BULLOCK. Fit chb urg, Mass. Correlation of Forces—A Meteorological Fact. MESSRS. EDITORS :—In connection with the theory of “Correlation of Forces,” some curious ideas are presented. In producing electricity by friction, for instan ce, it is evident that two surfaces should be rubbed t og e ther that will pro duce the most friction with the least heat. Whether tho old amalgam rubber and glass are the best for this purposo is doubtful. I would suggest that the well-known “biting” quality of turpentine or benzol e might be us ed to a dva n t age. Again: If two polished and plane surfaces of totally inelastic material are placed together, these might be /weed together with a pressure of any number of thousands of tuns by the bending of a hair, for, as there could be no motion, or heat, or electricity prod uced, the force applied might theoretically be multiplied or correlated into pressure simply to any extent. Many other curious notions grow o ut of the application of this beautiful the ory, the principlos of wh i ch ought to be understood by every inventor especially. But I have a fact to communicate in relation to meteorology. The early summer here, latitude 42°, was very wet. About the 1st of September commenced dry south winds, which ha ve blown, with occasi onal intermission, all the month. The first week I predi cte d an extraordinary ri se in the river, for I reasoned thus, both theory and previous observation bein g my guide : These winds take up a vast amount of moisture which must be precipitated on tlie higher and colder slopes of the Lake Superior dividing ridge, and of course come back to us til. the river. Thl';) l'imnit been Aiich ^ great and persistent rise as wfti never before known from the same cause. The Mississippi is within a few feet of the highest spring floods, and immense damage has been done in sweeping hay from the bottoms never before reached at this season.CHAS. BOYNTON. Lyons, Io wa. How to Clean Broom Corn Seed. MESSRS. EDITORS :—In your issue of September 11th, Benjamin Roach, of Natchez, asks for a seed cleaner for broom corn. A very good and simple one can be made by taking an old grain fanni ng mill, and in place of the arms, substitute a drum, 12 inches in diameter ; on the outside of this drum, nail strips all around, first driving through the strips 16 penny nails, after the manner of a thrashing cylinder ; take the broom corn by handfuls, and hold it to receive the action of these teeth while revolving ; two men can clean while one turns.A. D. C. New Madrid, Mo. Fh'es from Steam Pipes. MESSRS. EDITORS :—In regard to fires from steam pipes, I woul d say that I b ave been en gaged in repairing locomotives some years past, and it is well known that the jacketing of the boiler is matched p i ne wit h sheet-iron o ut side ; yet I have never seen any that looked burned. I have noticed some that looked like wood affected by dry-rot, and some of these boilers were worked with a head of steam o. 110 Ibs. I know also of a 24-horse power engine which has been running eighteen years, the cylinder of which is j acketed with pine, veneered. with rosewood, the wood of which is all sound. The same engine is run with from sixty to eighty pounds of steam, with only four feet of pipe from the boiler to the cylinder.C. B. HOYT. Oriskany Falls, N. Y. To Keep Pure Air in a Sid, Room, MESSRS EDITORS :—The following simple arrangement will remedy the evil of foul gas, generated by burning a kerosene lamp all night in a nursery or sick room. Take a raisin or any other suitable sized box, that will contain the lamp when set up on end. Place the lamp in the box, outside the window, with the open side fa ci n g the room. When there are blinds the box can be attached to each by leaving them a little open and fastening with a cord ; or the lamp box can be nailed to the window casing in a permanent manner. The lamp burns quite as well ow.tside, and a decided. improvement of the air in the room is experienced. Try it.” CONVALESCENT." Filing Saws. MESSRS. EDITORS :—In your article on “ How to file and set a saw,” nage 252, current volume, you say—” the teeth in cross-cut saws ought to cut both ways,” so they should; and I think they should cut much more in the downward stroke than in the upward, because in the latter we naturally have little more than the weight of the saw to bear on the wood, while in the former we work the saw inward and downward at the same time, with an extra force from the upper arm and shoulder. In filing, I pitch the teeth front a little, and give the front edge of the tooth a sharper bevel. It makes a great difference.E. R. BICE. Clinton, Mass. / [For the Scientific American.]