The president of the Metropolitan Fire Department, Gen. Shaler, has recently written a letter on the causes and prevention of fires. The season for the employment of all kinds of heating apparatus, and also for the increased' use of lighting materials has commenced, and as the careless use of such apparatus and materials is, perhaps, the most fruitful cause of fires, we deem it important to aid in giving currency to the opinions and valuable suggestions of Gen. Shaler. The most frequent cause of fires is considered to be the use of inferior kerosene oil. Gen. S.haler thinks no law can be enacted to reach personal carelessness in the use of this material, but suggests that those who sell it ought to be taught that " honesty is the best policy," by the infliction of severe penalties for the sale of any article of the kind which will vaporize below 100 degrees, Fahrenheit. To this suggestion every right-minded citizen who is acquainted with the subject, will say Amen! Gen. Shaler regards the present law, regulating the sale of such oils, as defective, and urges the passage of such laws by the incoming Legislature, as shall render the use of inflammable fluids comparatively safe. He mentions as' another frequent cause of fires " gas burn-el's, unprotected by globes or shades, in close proximity to window curtains. It is not uncommon to sec a side burner in workshops, and even in large warehouses, where the surroundings are light woodwork, without a guard or protection of any kind." With regard to means for extinguishing fires, he says, "The Commissioners are continually devising means by which fires may be reached at the earliest possible moment. The use of a portable fire extinguisher, carried by one man, for catching fires in their inception, was long since adopted ; and it is now under contemplation to multiply them throughout the city, wherever convenient and desirable locations can be found. The introduction of a new and perfect fire alarm telegraph, with alarm boxes located not more than two or three blocks apart, and accessible to citizens as well as policemen and firemen on street patrol, thereby securing the earliest possible notice of a fire, is quite certain to contribute greatly to the successful working of the Department. The establishment of a complete system of street patrols by firemen, having for its object the discovery and extinguishment of fires, was one of the earliest means adopted to reduce the losses by fire. " The heavy steam fire engines formerly used by the Department have been replaced by lighter ones. The horses have no difficulty in drawing these through the streets as fast as it is safe for them to travel. And as for the time consumed in hitching up, preparing to leave the houses, making connections to the hydrant after reaching the vicinity of the fire, stretching in and starting the water, under the present system of instruction, it is so incredibly short that the movements must be witnessed to be appreciated. Certain it is that no apparatus on wheels and worked by hand, however light and portable, such aa are used by Captain Shaw, in the London Fire Brigade, can get an effective stream of water on a fire in less time." The water is kept hot in the boilers and a run of a few blocks suffices to get up a working steam pressure. The facility and rapidity with which engines are started out is so great that Gen. Shaler avers he has witnessed the hitching up of a team, preparatory to leaving, inside of fifteen seconds, and it is not uncommon for a Company to perform all preliminary work and issue from its quarters in thirty seconds from the first sounding of an alarm. He says even " at night, when all but the patrols are in bed asleep, a company, favorably situated, that occupies more than a minute after receiving the alarm in leaving quarters, would be ashamed to acknowledge it." We feel sure that any one who has witnessed the prompt, rapid, and skillful evolutions of the members of the Metropolitan Fire Department in case of fire, will be willing to admit that a more efficient organization does not probably exist. The proof is, that except under rare and extraordinary circumstances, a fire is nevei; permitted to reach beyond the building in which it originates, and in a large number of cases it is checked before extensive damage accrues. And this is done without noise and bluster, and in the best manner to obviate unnecessary damage by flooding.