Volume II Part 27 (1/2)

What signifies philosophy that does not apply to some use? May we not learn from hence that black clothes are not so fit to wear in a hot sunny climate or season as white ones; because in such clothes the body is more heated by the sun alk abroad, and are, at the same ti on putrid dangerous fevers? That soldiers and seamen, who must march and labour in the sun, should in the East or West Indies have a uniform of white? That su that heat which gives headaches to many, and to some the fatal stroke that the French call the _coup de soleil_? That the ladies' summer hats, however, should be lined with black, as not reverberating on their faces those rays which are reflected upward fro a white cap of paper or linen _within_ the crown of a black hat, as soh it would if placed _without_? That fruit-walls, being blacked, may receive so much heat froree through the night, and thereby preserve the fruit froroith sundry other particulars of less or greater importance, that will occur from time to time to attentive minds

B FRANKLIN

_To the same_

ON THE EFFECT OF AIR ON THE BAROMETER AND THE BENEFITS DERIVED FROM THE STUDY OF INSECTS

Craven-street, June 11, 1760

'Tis a very sensible question you ask, how the air can affect the baro appears covered ood? If, indeed, it was so closely covered as to admit of no communication of the outward air to the surface of the ht in the air could not possibly affect it But the least crevice is sufficient for the purpose; a pinhole will do the business And if you could look behind the frame to which your baro

There are, indeed, some barometers in which the body of the , and so the air cannot come into immediate contact with the mercury; yet the sa flexible, when, the bag is pressed by any additional weight of air, it contracts, and the hter and its pressure less, the weight of the

Your observations on what you have lately read concerning insects is very just and solid Superficial minds are apt to despise those who make that part of the creation their study as ed to theement of man, the labours of the little silkworm afford employment and subsistence to thousands of families, and become an immense article of commerce The bee, too, yields us its delicious honey, and its wax useful to a multitude of purposes Another insect, it is said, produces the cochineal, from whence we have our rich scarlet dye The usefulness of the cantharides, or Spanish flies, in medicine, is known to all, and thousands owe their lives to that knowledge By human industry and observation, other properties of other insects may possibly be hereafter discovered, and of equal utility A thorough acquaintance with the nature of these little creatures may also enable mankind to prevent the increase of such as are noxious, or secure us against the s doubtless your books make mention of: I can only add a particular late instance, which I had froreen ti's yard in that country, a kind of worms was found, which every year became more nureatly dareat naturalist, from Stockholm, to inquire into the affair, and see if the mischief was capable of any remedy He found, on exa, deposited in the little roughnesses on the surface of the wood, by a particular kind of fly or beetle; froan to eat into the substance of the wood, and, after soain a fly of the parent kind, and so the species increased The season in which the fly laid its eggs Linnaeus knew to be about a fortnight (I think) in the month of May, and at no other time in the year He therefore advised, that soreen timber should be thrown into the water, and kept under water till the season was over Which being done by the king's order, the flies,the usual nests, could not increase, and the species was either destroyed or went elsewhere: and the as effectually preserved, for after the first year it became too dry and hard for their purpose

There is, however, a prudent e of nature may be ornamental, and it lect the knowledge and practice of essential duties, we deserve reprehension For there is no rank in natural knowledge of equal dignity and iood husband or wife, a good neighbour or friend, a good subject or citizen, that is, in short, a good Christian Nicholas Gilected the care of his family to pursue butterflies, was a just object of ridicule, and we ame to the satirist

B FRANKLIN

_To Dr Joseph Priestley_

EFFECT OF VEGETATION ON NOXIOUS AIR

That the vegetable creation should restore the air which is spoiled by the animal part of it, looks like a rational system, and seems to be of a piece with the rest Thus fire purifies water all the world over

It purifies it by distillation, when it raises it in vapours, and lets it fall in rain; and farther still by filtration, when, keeping it fluid, it suffers that rain to percolate the earth We knew before that putrid anietables when mixed with the earth and applied as manure; and now, it seems, that the same putrid substances, , thriving state of your mint, in putrid air, see froive sorow near houses, which has acco, fro unwholeso unhealthy in the air of woods; for we Americans have everywhere our country habitations in the midst of woods, and no people on earth enjoy better health or are le_

ON THE DIFFERENCE OF NAVIGATION IN SHOAL AND DEEP WATER

Craven-street, May 10, 1768

You ether in Holland, you rees went slower than usual, and inquired of the boatht be the reason; who answered, that it had been a dry season, and the water in the canal was low On being asked if it was so low as that the boat touched the muddy bottom, he said no, not so low as that, but so low as to make it harder for the horse to draw the boat We neither of us, at first, could conceive, that if there ater enough for the boat to swi deeper would make any difference; but as thethees was likely to make such difference, if any there were, more readily observed by theularly and constantly backward and forward in the sa in it, and attempted to account for it fro the canal, th of her course move out of her way a body of water equal in bulk to the room her bottom took up in the water; that the water so moved et behind her; that if the passage under her bottom was straitened by the shallows, more of that water must pass by her sides, and with a swifterthe contrary way; or, that the water beco lower behind the boat than before, she was pressed back by the weight of its difference in height, and her ht constantly to overco for uncertain facts, I determined to make an experiment of this when I should have convenient tiland, as often as I happened to be on the Thames, I inquired of our water over shallow or deep water I found thereat difference, but they differed widely in expressing the quantity of the difference; so it was equal to a mile in six, others to a mile in three, &c As I did not recollect to have met with any mention of thisthat if the difference should really be great, it ht be an object of consideration in the able canals in this island, I lately putthe experi h of planed boards fourteen feet long, six inches wide, and six inches deep in the clear, filled ater within half an inch of the edge, to represent a canal I had a loose board, of nearly the saht be sunk to any depth, and fixed by little wedges where I would choose to have it stay, in order tothe surface at the sah I had a little boat in for, two inches and a quarter wide, and one inch and a quarter deep When swiivesilk thread to its bow, just even with the water's edge; the other end passed over a well- freely on a s the boat at one end of the trough, the weight would draw it through the water to the other

Not having a watch that shows seconds, in order tofrom end to end, I counted as fast as I could count to ten repeatedly, keeping an account of the nuers And as much as possible to correct any little inequalities in , I repeated the experiht take theare the results:

Water 1-1/2 inches deep 2 inches 4-1/2 inches

1st exp 100 94 79 2d ” 104 93 78 3d ” 104 91 77 4th ” 106 87 79 5th ” 100 88 79 6th ” 99 86 80 7th ” 100 90 79 8th ” 100 88 81 --- --- --- 813 717 632 --- --- --- Medium 101 Medium 89 Medium 79