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"TAE. Marine. REVIEW FOWNES' DESIGN OF STERN FRAME. circular from immediately below the arch down to the base. Instead of any welding, the post is shrunk into the bottom keel piece. The gudgeons are also portable, and they are shrunk on to 'the -circtlar. back. post and keyed in addition. These innovations have been introduced so that the en- *tire frame may be the more expedi- tiously manufactured. Under this sys- tem the various parts in course of manufacture may be distributed over the several machines, and continuity of machine work is thereby main- tained until such time as the various pieces are ready for finally fitting to- gether. It is also claimed that rapid repairs are greatly facilitated, inas- much as a new bottom piece or back post may be provided without the ne- cessity of having to cut out the entire stern frame from the vessel, and sim- ilarly, as the portable gudgeons of damaged vessels can be conveniently replaced without the back post having to be condemned, as is the case with stern frames of other design. In the Fownes design there has been intro- duced the method of shrinkage in sub- stitution for the older method of welding, which is slower, as only one set of men can be working on any particular, job at the same time. This design of stern frame,*it is stated, has received the approval of all the various classification societies. SPEAR PROPELLER DESIGN. In studying the subject of wave motion as occurs in any fluid medium such as water or an allied substance, the air, the inventor of the propeller shown in the accompanying illustrations noted the fact when waves are set in motion or currents formed they have been pro- duced the most quickly and with the least loss of power where the opposing or actuating surface which causes this motion is curved with the conchoidal curve. As a curved surface of this de- scription can from its nature present no focus or center for converging air waves or liquid waves, as of water, but distrib- utes such waves or currents without so doing, 1. ¢., . focusing them, it . has seemed best suited to the inventor's pur- pose in the construction of his propeller blades. Its utility may be readily shown by forming an ear trumpet in such man- ner that the passage through it shall be of this conchoidal shape, that is, substan- tially the shape of the passages from the exterior to'. the interior of a conch shell, and comparing its efficiency with the efficiency of any of the ear trum- pets of ordinary construction. ao (The reason for this, as the inventor believes, is that there is practically no chance for interference between the various waves which are received at the embouchure, or bell mouth entrance, of such ear trumpet, and are conveyed along therefrom to the small opening made for application to the external canal of the ear. In such cases aerial vibrations with- in the ear trumpet may be considered as conveyed towards the smaller end with- out meeting with or obstructing the pas- sage of similar vibrations taking the same course. The invention is based upon the application' of this same discovery to the construction of propellers, and consists in a propeler provided with two or more blades, one or both surfaces of which blades are conchoidal Fig. 1 is an end elevation of a pro- peller embodying the invention; Fig. 2 being a side elevation thereof, and Fig. 3 a top view. The blades are preferably made with a double curve, one-half of © the. blade projecting forward and the other half rearward in order that the blade may be equally efficient whether it is working foward or backward. In any - case the peculiarity of the blade is such that its working surface being conchoidal in shape the particles impinging upon it are forced from its surface practically in one given direction, that is, in a con- stantly increasing and diverging direction from each other without interference, and hence with but slight resistance other than that due to friction against the blades.