One of ttie characteristics of the present ago, is the constant effort to improve the articles in daily use in our dwellings and offices, and to add to our household conveniences and facilities for the transaction of business. The writing desk has received its full share of attention from inventors, but the idea of rendering its upper surface a means of something more than mere support for documents, and a plane on which to write, seems to have been heretofore somewhat overlooked. The object of this invention is to combine the advantages of the smooth top with those of a surface which will, at the same time, answer the purpose of a slate or blackboard, on which temporary writing and figuring may be performed with the ordinary crayon or slate pencil. The feature of this invention which has been made the sub-ject of patent, is the adaptation of a slate surface to the tops ot desks, for schools, counting rooms, or for any other purpose [or which such desks may be desirable. For schools the use of this desk obviates the breaking of slates and the expense of replacement, and what is a still more important consideration, obviates much of the noise in schoolrooms attending the use of loose slates, and the marring of the tops of ordinary desks by the attrition of slate irames. The illustrations we give of different patterns of this desk, show them to be tasteful in design, and also exhibit fully the application of the improvement. The composition used is equal in hardness and smoothness to the stone slate, while at the same time they retain figures better. The latter are however, readily removed by a damp cloth or sponge. These desks have been introduced into some counting rooms in this city, and we understand give good satisfaction. In commercial schools and colleges, they would be of special service, as they can be used with great advantage in teaching writing and book-keeping. For mechanics who frequently wish to draw temporary plans they are also very useful. Two patents have been obtained on this desk, and a reissue is now pending. The surface may be made of stone slate as well as composition, but the composition is more convenient to apply, and is considered superior in other respects. Manufacturers and dealers in school and counting-house furniture would do well to give attention to this improvement. The inventor, Mr. W. W. Levering, may be addressed, at 35 and 37 Park Place, New York city, and he is ready to negotiate with parties desirous to obtain rights to manufacture. Patent Office Affairs. Commissioner Fisher has given his decision in the case of the TIeck thread dressing patent, an extension of which was asked. The application was rejected on the ground that the invention was not new at the time the original patent was applied for, and that the patent should never have been issued. Extension have been granted in the following cases : Stevens, Crosby, and Pearson, of Boston, for a seed planter. Thomas J. Silsby, administrator of Arad Woodruff, of Boston, for improvement in machinery for spinning, and to Thomas J. Knapp, for an adjustable tenoning tool. The senior member of the Board of Examiners-in-chief, Mr. Hodges, who acts as Commissioner in the absence of that officer, has heard the argument and given his decision upon the following application for extensions of patents : Jacob A. Connoyer, of New York, for a wood-splitting machine; George W. Brown, of Galesburg, Illinois, for a corn planter. Mr. Hodges in both cases granted the extensions prayed for. The Commissioner having been employed as counsel in lawsuits in which these parties were interested, left the office temporarily in the charge of Mr. Hodges, while these parties were before it. It was from parties interested in the latter case that the telegram was sent to Senator Trumbull to prevent Colonel Fisher's confirmation, stating that he was employed as counsel in five cases involving several millions of dollars. F. W. Patter has been promoted from a clerkship to Second Assistant Examiner, and assigned to Professor Hedrick's class of chemicals, and James L*upton, of Ohio, has been appointed second class clerk. Peter Nodine has been appointed machinist and superintendent of the model room, vice Cornelius Jacobs, removed.