We have had many long letters on various subjects during the past week, and as we cannot insert them all in full, we will endeavor to give the pith of those which are likely to prove of interest to our readers. Two communications on dialling first meet our attention. G. W. Hildreth, of Lockport, N. Y., after having had a sundial for thirty-five years, and now possessing three, tells us that the one he considers preferable and best ie constructed as follows :—The hour circle should be movable, and set by a scale, so that the dial will give true clock time. One of these scales he encloses to us; it contains the clock's variations for every day in the year, and is now pasted up in our editorial room. He also describes the manner in which he constructs his sundials, and we have no doubt he will give the same information to \ any of our readers who wants to make one, and he adds a postscript stating that charcoal has been used for burns in his neighborhood for more than twenty years. Thomas Russell, of New York, suggests that dials are only accurate when they are graduated to the exact latitude in which they are placed, and the tables which are given in books are only to be used as examples, so that by them any one can make the necessary alterations in the graduation of their circles to suit the latitude in which they live. In our large country this is necessary, as the time varys much, being one hour and a quarter between this city and St. Paul, Minn. James Bird, of Plankville, La., gives us in a pretty and simple essay (which is written so pleasantly that you almost think a bird sang, rather than wrote it, and which he says is his first attempt), the reason why one little puff of steam separates from the main body issuing from a steam engine, and commences whirling in the air. It is because that small puff has a greater affinity for the air than the rest, says our songster. Try again, James Bird. Ira Parke, of Hudson, Wis., prevents the moths from attacking his bee hives by mounting them on legs a little crooked, and placing these on little blocks during the warm weather. He also informs us that he had two hives, in one of which the bees were in a fine healthy flourishing condition, and the other was deserted by all save the queen and two faithful attendants. By changing their places, he got the bees from the strong hive to go into the poor one, and so equalized the number of bees in each hive for the winter, as the experiment was tried in the fall. Dr. Hill, of Galesbury, 111., objects to some remarks made by us on saleratus, and very truly observes that cooks do not understand the laws of chemical combination, and consequently overdoes the bread with saleratus. They also use much sour milk, and have to put a large quantity of saleratus in to neutralize its effect, so that we do not have simply the tartarate of potash which is common to wine as well as bread, but the lactate of potash which produces indigestion, sick headache, and other ills. The difference between us and the foreign wine drinker is, that they drink an acid tartarate, and we eat an alkaline or neutral tartarate or lactate, so that they are the " sour" set, and we are not " sweet," but "alkaline." Far better would it be if all foreign substances, except salt, were left out of bread and biscuits. The clerk of Tiger Engine Company, of Haverhill, Mass., requests us to publish the fact that these ferocious animals on July 19th played as follows:—Fifty men drew water through three lengths of suction pipe up a rise of fifteen feet, forced it through two hundred feet of hose and one inch nozzle, five feet over a flag staff 183 feet 7 inches high, or from the water 203 feet 7 inches. This was remarkably good playing, and does the Tiger b'hoys credit. The " machine" was built in 1*51, by W. Jeffers, of Pawtucket, R. I.