MAGNETIC VARIATION The Didulh Minnesotian, says: The magnetic compass, on the north shore of Lake Superior and particularly in surveying around Duluth, is a very zigzag kind of guide The Assistant Surveyor in charge of the transit on our Town Site Survey during the past week expe i rienced some of its wildest eccentricities of variation In running and cutting out a transit line between sections on the mountain side, at a certain spot he noticed in a distance of fifty feet a change from 11 deg east, to 17 deg east; then in a hundred feet further, back to 12 deg east; while five hundred feet further on from 12 degs 30 min east it whirled around to 30 degs west (!) and kept at that for three hundred feet and then got back again to 11 degs east The Surveyor ! picked up a piece of rock of the granitic species, which seemed to prevail in the locality, and applied it near his compass, when the needle followed it around the same as it would a true loadstone The general Government may well require the use of the solar compass in surveying lands in this region The needle is but a blind guide WE are reminded, says the American Builder, that, during the past month, a letter came to us from a distant city in which the writer suggests a novel style of a dwelling, and asks us whether we think the plan patcntable Most assuredly we do, and we hail this request as an encouraging sign of the times Why no patents are applied for on improvements in dwellings, has, to us, long been a mystery We want something new What are our inventors about ? Millions of money expended annually in the construction of dwelling houses and no patent house Start in, inventors You will produce a sensation among the dry bones in the architects offices, that will be eminently amusing We beg of you not to consult any books on architecture; but go at it in a muscular style and give us an original plan for a house If the dead centuries, surfeited with architectural lore, see fit to laugh at you, do not be disturbed An age that lays cables across an ocean, and railroads across a continent, can afford to be laughed at Send on your plans THE Gates head (Eng) Observer says that the offering of prizes to pit lads in that district to induce them to sea,rch for fossil remains has been attended with unexpected results Not only had the lads picked up from the refuse shale heaps large numbers of fish remains, and some remains of large reptiles, but what is really extraordinary, and will astonish palaeontologists, one of the lads has found the lower j aw of a true mammal The effect of this discovery will be to reduce the comparative ages o{ all hitherto known mammalia, and carry backward the mammalian life of the world to a much earlier period than that at present assigned to it To INVENTORSWe desire to call the attention of inventors to an article entitled " Invention," published in another column, and copied from the New York Triliwne This able article forcibly confirms the views we have always maintained in our paper, that there is no natural limit to invention any more than to the desires of individuals for new and improved articles, machines, and processes We also advise all who have or expect to have patents or patented articles for sale to read attentively an able communication entitled, " Printers' Ink in the Sale of Patented Articles" It contains most valuable suggestions Wl 11 HATNIE, of Sacramento, who has a large number of silkworms, lost 500,000 in one night He attempted to hatch them by artificial heat, and to economize the heat by running steam pipes through the building THE GUNPOWDER HAMMER, for driving piles, illustrated in our last issue was patented by Thomas Shaw, of Philadelphia It is a very useful and ingenious machine, and the inventor's name should be associated with its introduction NitroGlycerln Explosion The Titusville (Pa) Herald records a singular accident: " One of the most extraordinary accidents it has teen our province to chronicle, occurred at the ' Salt Well/ Scrubgrass, on Friday afternoon, July 30th, and resulted in the death of George W Fetterman, and the seriously wounding of two other persons " The unfortunate man procured on Monday last, for the purpose of oiling engines, a quantity of thick fluid which, from the color, he supposed to be lard oil, but which, as the sequel proved, was really that dangerous explosive, nitroglycerin He used it as a lubricator on the engine at the ' Salt Well,' and also on another engine, from Monday until Friday afternoon Strange as it may appear, the nature of the fluid was not suspected during all the time, although it was remarked by some one who was curious enough to taste it, that it was singularly sweet for lard oil However, about 3 o'clock on Friday afternoon, as the man was oiling the gudgeon of the sandpump pulley, which was revolving with great rapidity, a terrific explosion occurred Fetterman was blown some distance and instantly killed He was mutilated almost beyond recognition The flesh was literally torn from his limbs, and one half of his head was blown off His brother James and a man named D McNally, who were standing near by, were thrown violently to the earth They were both much bruised The former was wounded in the chest, thigh, and groin by pieces of the can, in which the glycerin had been kept, and other splinters, and the latter was struck in the face by a piece of tin Their injuries are not considered dangerous " The force of the explosion drove pieces of the can and splinters in all directions, and also blew three or four boards off the enginehouse One piece of tin was driven entirely through a fourinch post At the time of the explosion there was very little glycerin in the can, probably not more than an ounce or two"