The interest in the velocipede continues nnabated. A *' Long Island rider " writes us a description of an improvement which strikes us as being novel at least. It is a device to enable velocipedestrians to use the ordinary horse-car tracks as a way for their machines. The attachment is a bar of iron or rather a rod about of an inch in diameter with a small wheel at the end, remote from the velocipede proper, and having the other end attached to the " back-bone " of the machine. The small wheel bears on the opposite rail from the one in which the velocipede wheels run, and thus acts as a brace, and prevents running off the track. He says it has been tried with complete success ; the machine being propelled with very little effort, and running up a grade with ease and rapidity. These attachments will soon be offered for sale. The Journal of the Telegraph proposes that telegraph messengers be supplied with velocipedes for the more rapid delivery of messages. It says : '* The messengers of a company perform a most important part of the telegraphic service. Their service demands a high degree of fidelity, sagacity, determination, beside the mere swiftness of foot necessary to perform their duty acceptably. But there is more practical skill and more persistant watchfulness needed to reduce the time which is even now expended between the reception of a message by the wire and its delivery into the hands of the party addressed, than in all the other parts of its progress. Anything which will reduce the time thus consumed, which will prevent the consumption of an hour or more to deliver a dispatch two miles from a central office which came a thousand miles over the wires in two minutes, must be hailed as an acquisition, and, if possible, made available. " Well,' we shall see what we shall seeJ by-and-by. We would like to see the experiment tried. Ponies were once tried in St. Louis, with what success we do not know. We want to see a good boy straddled across a velocipede and put on his honor and metal. We think there would be some quick time made." An exhibition of a ladies' velocipede took place at Hanlon's Hall on Tenth St. on the evening of the 24th of March. It differs from the ordinary machine in having the perch lower, and in the arrangement of the spring, making it more convenient to mount and dismount. Instead of a saddle, there is a seat of wicker work neatly woven. The fore wheels are about thirty-two inches in diameter. Two of these machines were exhibited, ridden by two graceful'young ladies, who drove the cranks with both feet, in the same manner as men. They were dressed in a very becoming costume of dark woolen stuff, tlieir skirts being divided at the bottom, and buttoning around the ankles, not unlike the trowsers of a Zouave, and exposing the neatest foot and Chaussyre that can be imagined. Their gloves were of the same hue as their dress; one wore ribbons and facings of blue and the other of pink. They rode with much skill and elegance as well as strength, and, with the assistance of Mr. Pickering and Mr. Brady, went through with a number of intricate and pleasing figures, in the presence of a large number of ladies and gentlemen, who loudly testified their applause. We have no doubt that this velocipede will come into extensive use among the ladies, who will find it an attractive means of healthful exercise, in halls set apart for the purpose. A Utica correspondent writes us as follows: " Your veloci-pedic readers may like to have a ready means of determining their speed. The following method is nearly accurate, not varying from the fact more than two feet two inches in a mile. Divide 336, by the diameter in inches of the driving wheel; the quotient will be the number of revolutions per minute, which will produce a speed of one mile an hour. 336*135245, will give the result more exactly, but 336 is near enough for all practical purposes. " Thus with a 4-foot wheel, 7 revolutions a minute give a speed of a mile an hour, 70, of ten miles an hour/* A correspondent* of Toronto who subscribes himself " Unfortunate " makes some good suggestions He says : " I have been watching the velocipede notes in your valuable Journal for some time past in the hope of learning that one of these marvelous machines had been invented especially i i adapted for the infirm and crippled portion of the community, ' but up to the present time of writing I have discovered noth- j 1 ing suitable. The late war has caused the loss of many a leg ' and in this age of machinery, the number of maimed persons is increasing. To lighten the lot of this unfortunate class is surely worthy of some thought; many of your ingenious con-1 tributors will I am sure, be glad to turn their attention to it, i j 1 11 ] 1 from motives of humanity and not profit. The loss of a leg, I replaced by never so shapely an artificial one, incapacitates a j man from almost every employment by reason of the difncul-1 ty he experiences in moving about. I am aware that there is at present a machine with a crank in the axle used by persons whose pedal extremities have become paralyzed but the effort required for propulsion is very great. I would suggest the construction of a velocipede that could be worked jointly by one foot and one hand or by the hands alone, or the motion might be taken from the shoulder perpendicularly with advantage, the one foot being used for steering. I am not a mechanician and merely throw this out as a hint to any good Samaritan who will take the matter up. We give herewith an engraving of a two-seated bicycle j which will interest our readers. This machine, designed by H. P. Butler, of Cambridge, Mass., seems entirely practicable. The engraving shows the parts so clearly that a detailed description is unnecessary. We may add, however, that the back seat is intended to be used either as a side saddle for ladies, as shown in the engraving, or an ordinary saddle for gentlemen, both riders assisting jn the propulsion. The inventor also has in view the placing of two side saddles over the rear wheel, to accommodate two ladies, who could then assist in propelling the machine. Several leading firms in Newark, N. J., heretofore engaged exclusively in the manufacture of elegant carriages, have begun the manufacture of velocipedes for New York firms, while other establishments are rapidly turning off the wheels and iron works to supply the trade in other cities. An inventor in New Albany, Ind., is making a new locomo- , tive apparatus. It consists of a pair of. skates on the bicycle order, the wheels being five inches in diameter and three-fourths of an inch wide, fastened to wood, which are to be '. strapped to the feet. The wheels are made large and broad, in order that the wearer may have no difficulty in passing over rough pavements at a rapid rate. We understand that the prices are gradually coming down ; at the halls of instruction, the result of the competition that ' has arisen. As a counter influence, however, upon the rates demanded, the increasingnumber of those desiring instruction still enables the proprietors of these places to make large profits Remarkable Millstone Explosion. A correspondent from Leesburg, Mississippi, writes us an account of a remarkable explosion which occurred, March 2d, in an adjoining county under somewhat mysterious circum stances. The millstone was a patent French burr of about 30 inches diameter, considerably worn, having been run for years. The i burrs were encased in cast-iron beds and were driven by j steam power. The mill liad not been in operation more than I ten minutes before the fatal accident occurred. The miller was regulating the mill, and finding that it was running too slow, he ordered the engineer to give it more speed! but before fch e order was complied with, the explosion took place with berrible effect, scattering the fragments of stone in every direction, killing the miller instantly, and wounding five other hands employed about the mill. The report of the explosion was heard at a distance of four miles. We are requested to give our opinion of the cause of this explosion, which can be accounted for in no other way than either the accidental or malicious introduction of some explosive compound into the grain, which was exploded by the friction of the stones. The loud explosion points clearly to this conclusion, and as it is by no means probable that anything of the kind could have been the result of accident, an effort ought to be made to discover whether or not it was the work of some malicious fiend, in human shape, instigated by motives of revenge, or otherwise.